A veces me sale bien multiplicar, pero todavía me cuesta dividir con decimales.

Both are possible, but they are not exactly the same.

Multiplico bien means I multiply well. It sounds more direct and more like a general statement about your ability.

Me sale bien multiplicar is more idiomatic and literally means something like multiplying goes well for me or I manage to do multiplication well. It often feels a bit less absolute and more about how the activity turns out in practice.

That fits well with A veces: sometimes it goes well, sometimes not.

Here, me is an indirect object pronoun, meaning to me or for me.

• me sale bien = it goes well for me
• me cuesta = it is difficult for me

So me is not there because the speaker is doing something to themself. It marks the person affected by the action or experience.

No. In this sentence, me sale is not reflexive.

A reflexive verb would mean the subject does something to themself, like me lavo = I wash myself.

But in me sale bien, the verb is salir, and me means to me / for me. It is better understood as an idiomatic structure: something turns out well for someone.

Because the thing acting as the subject is the whole activity multiplicar, and an infinitive used this way is treated as singular.

So:

• Multiplicar me sale bien
• Dividir con decimales me cuesta

Each infinitive phrase is treated like one single activity, so the verb stays in third person singular:

• sale
• cuesta

In Spanish, the infinitive is often used to talk about an activity in a general way, similar to English multiplying or to multiply.

So:

• multiplicar = multiplying / to multiply
• dividir = dividing / to divide

After verbs and expressions like costar, gustar, interesar, or salir bien, using the infinitive is very common when you mean the activity itself.

Because Spanish often uses the bare infinitive to talk about an activity in general.

So multiplicar and dividir here mean the activity of multiplying/dividing, without needing el.

You can sometimes see el + infinitive in Spanish, like el fumar es malo, but that is more formal, more abstract, or stylistically marked. In everyday speech, me cuesta dividir sounds much more natural than me cuesta el dividir.

Here todavía means still.

So todavía me cuesta = it still costs me effort / I still find it difficult.

Yes, aún can often be used in the same way:

• pero todavía me cuesta...
• pero aún me cuesta...

In everyday Spanish from Spain, todavía is extremely common and sounds very natural.

It means with decimals or involving decimal numbers.

In context, dividir con decimales means doing division where decimals are involved. For example, division problems like 3.6 ÷ 1.2.

A more explicit version could be:

• dividir números decimales
• hacer divisiones con decimales

But dividir con decimales is perfectly understandable and natural in a school or maths context.

Yes, absolutely. Se me da bien multiplicar is very natural and common.

It means I’m good at multiplying.

The difference is mainly one of nuance:

• me sale bien multiplicar = multiplying goes well for me; I manage it well
• se me da bien multiplicar = I’m good at multiplying as an ability

In your sentence, me sale bien works especially well because of A veces. It suggests that sometimes the result comes out well.

Because pero joins two contrasting clauses, and in standard Spanish it is normal to put a comma before it.

Here the two parts are:

• A veces me sale bien multiplicar
• pero todavía me cuesta dividir con decimales

The comma helps mark the contrast between sometimes I do well at one thing and I still find the other thing difficult.

Yes, Spanish word order is flexible, but some positions sound more natural than others.

• A veces me sale bien multiplicar is the most neutral and natural.
• Me sale bien multiplicar a veces is possible, but it sounds a little more marked.
• Todavía me cuesta dividir con decimales is also the most natural order.
• Me cuesta todavía dividir con decimales is possible, but less neutral.

So learners should usually stick with the version in the sentence unless they have a specific reason to emphasize something.

Because bien is modifying the verbal idea salir bien, which is a very common fixed combination meaning to turn out well.

So:

• me sale bien = it goes well for me / it turns out well for me

You could also hear:

• Multiplicar me sale bien

That just moves multiplicar to the front for emphasis. But me sale bien multiplicar is a very natural order in conversation.