kaado no meisai wo mitara, sensyuu no hirugohan no daikin mo haitte imasita.

カードの明細 means the card statement or the itemized statement for the card.

• カード = card, usually a credit card or similar payment card in this kind of sentence
• 明細 = details, breakdown, itemized statement

So カードの明細を見たら means when I looked at the card statement.

The particle の connects nouns and often works like of or shows that one noun describes another.

So:

• カードの明細 = the statement of the card → more natural English: the card statement

This is a very common noun-linking pattern in Japanese.

を marks the direct object of the verb.

• 明細 = the statement
• 見る = to look at / to see

So 明細を見たら means when I looked at the statement.

見たら is 見る in the past + たら form.

Here, たら often means:

• when
• after
• sometimes if

In this sentence, it has a discovery feeling:

• When I looked at the statement, I found that...
• After checking the statement, it turned out that...

So 見たら is not just a plain sequence of actions. It often suggests that something was noticed as a result.

This is a chain of nouns connected by の.

Break it down like this:

• 先週 = last week
• 先週の昼ご飯 = last week’s lunch
• 先週の昼ご飯の代金 = the cost/charge for last week’s lunch

Japanese often stacks nouns this way, and the final noun is the main thing:

• the main noun here is 代金 = charge / cost / payment amount

So the whole phrase means the charge for last week’s lunch.

They all can refer to lunch, but the nuance is a little different.

• 昼ご飯 / 昼ごはん = lunch, midday meal
• ランチ = lunch, often used for eating out, lunch sets, or a more casual modern feel

昼ご飯 sounds very normal and everyday. Writing it as 昼ごはん instead of 昼ご飯 is just a spelling choice; both are common.

代金 means the price, the charge, or the amount owed for something.

• 代金 is more specific: the money for a particular purchase or service
• お金 just means money in general

So:

• 昼ご飯の代金 = the charge for lunch
• 昼ご飯のお金 would sound less precise and less natural here

も means also, too, or sometimes even.

Here it shows that the lunch charge was included as well.

The nuance is something like:

• The charge for last week’s lunch was in there too
• Even the charge for last week’s lunch was included

It suggests that this is one item among others on the statement.

入っていました comes from 入る, which literally means to enter or to be in.

In this context, it means:

• was included
• was on it
• was in there

So 代金も入っていました means:

• the charge was included too
• the charge was on the statement too

Japanese often uses 入る for things being contained in a list, package, bill, report, or statement.

The form 入っていました is 入っている in the past polite form.

• 入っている = is included / is in there
• 入っていました = was included / was in there

This often describes a state that existed at that time.

So the sentence is not focusing on the moment something got added. It is describing the state of the statement when the speaker checked it:

• When I looked at the statement, the lunch charge was included.

All of these can appear in related contexts, but they are slightly different.

• 入っている = is included / is in there
• ある = exists / there is
• 載っている = is listed / appears in print or on a page

In a statement or bill context, 入っている sounds very natural because it emphasizes that the item was contained in the statement.

• 明細に入っていました = it was included in the statement
• 明細に載っていました = it was listed on the statement

Both can work, but 入っていました feels a little more like it was part of the total contents.

Japanese often leaves out subjects and other information if they are clear from context.

In this sentence:

• the person who looked at the statement is understood from context
• the thing that was included is 先週の昼ご飯の代金
• the place where it was included is the card statement

So even without an explicit subject, the sentence is perfectly natural in Japanese.

Yes, there can be.

Two parts help create that feeling:

• 見たら often suggests when I checked, I discovered that...
• も can suggest too / even

So the sentence may imply something like:

• When I looked at the card statement, I saw that even the charge for last week’s lunch was in there too.

Depending on context, the speaker may be mildly surprised, annoyed, or simply noting it.

Yes. Japanese is normally written without spaces.

The standard writing would be:

カードの明細を見たら、先週の昼ご飯の代金も入っていました。

The spaces in learning materials are just there to make the structure easier to see.