Can I use the word "task" for this:

"If John has got 5 apples and Tom has got 7 apples, how many apples do they have together?"

Can I say, "Please solve this task" or "Preparing for the exam, I solved a lot of tasks"?

During a test in maths you have to do several of these.

But how do you call them? And what do you do with them?

You can solve an equation but it looks like this:

6+7= ?