Learn Hardcore Russian: Мы увеличим количество задач завтра, но оставим последний пример таким же простым, как раньше. - We will increase the number of tasks tomorrow, but we will keep the last example just as simple as before.

Because увеличим (from perfective увеличить) presents a single, completed action in the future: “we will increase (once, to completion).” The imperfective увеличивать uses the compound future (будем увеличивать) and focuses on an ongoing/repeated process: “we will be increasing / will keep increasing.” Here the plan is one increase tomorrow, hence perfective.

Why количество задач? What case is задач?

Количество governs the genitive, so its complement is in the genitive plural: задач (from задача). This is a standard pattern:

количество людей
количество ошибок
количество идей

Can I say число задач instead of количество задач? Any nuance?

Yes. Both are idiomatic.

число задач = the numeric count; a bit more “count-like.”
количество задач = quantity/amount; the most neutral and common choice. In most contexts, they’re interchangeable here.

What’s the difference between задача and задание?

задача: a task/problem to solve (often a problem, e.g., a math problem).
задание: an assignment/instruction you are given to complete. So you might say количество задач for problems, or количество заданий for assigned tasks.

Is мы necessary? Can it be dropped?

It’s optional. Russian verb endings show the person/number, so Увеличим количество задач завтра... is still clear. Мы adds clarity or emphasis.

Why is there a comma before но?

Но links two independent clauses, and Russian puts a comma before such coordinating conjunctions:

Clause 1: Мы увеличим количество задач завтра
Clause 2: (мы) оставим последний пример...

Could I use а instead of но?

Yes, with a nuance:

но = “but/nevertheless,” stronger opposition.
а = “but/whereas,” milder contrast. Both work here; но highlights the concession more strongly.

What does оставим mean here—“leave” or “keep”?

It means “keep/leave (something) in a given state.” With an object + predicate adjective, оставить commonly means “to keep”: оставим последний пример простым = “we’ll keep the last example simple.”

Why is it таким же простым, not такой же простой?

After verbs like оставить/сделать/считать, the predicate describing the object’s state takes the instrumental case. The object is последний пример (masc. sg.), so the predicate is masc. sg. instrumental: таким же простым.

Мы сделали упражнение лёгким.
Она считала задачу сложной.
Оставим текст коротким.

What does же add in таким же? Is this the same as также?

таким же = “the same (kind of), just as,” used with comparisons: таким же простым, как...
так же (two words) = “in the same way/as,” typically with как.
также (one word) = “also/too,” and is not used here. Here же reinforces exact sameness. Don’t confuse так же/таким же with также.

Do I need и in как (и) раньше?

Both are fine. как и раньше is very common and a bit more explicit; как раньше is slightly more concise. Meaning is the same: “as before.”

Is the comma before как раньше required?

Yes. This is a comparative clause after a correlative construction (таким же ... как ...), so standard punctuation puts a comma: ... таким же простым, как раньше.

Can I move завтра elsewhere?

Yes. Time adverbs are flexible:

Завтра мы увеличим количество задач...
Мы завтра увеличим количество задач...
Мы увеличим завтра количество задач... (less common but possible) The meaning stays the same; word order tweaks emphasis.

Can I say Мы увеличим задачи завтра to mean “increase the number of tasks”?

Avoid that. увеличить задачи tends to mean “make the tasks bigger/more extensive.” To express “increase the number of tasks,” use:

увеличить количество задач
увеличить число задач Colloquial: сделать задач больше.

What case is последний пример here?

Accusative as the direct object of оставим. For inanimate masculine nouns, accusative = nominative: пример. The adjective последний agrees (masc. sg. acc. = masc. sg. nom.).

Could I use сделаем instead of оставим?

оставим ... простым = “keep/leave it simple” (it’s already simple; you won’t change that).
сделаем ... простым = “make it simple” (you will change it to become simple). Choose based on whether you’re maintaining the current state or creating it.