How do teachers ask to calculate expressions?

Solution 1:

As a third grade teacher in the US (in the 1970s), I variably would asked

What is 2 + 3?
How much is 2 + 3?
Add 2 + 3. How much?
2 + 3 is what?
What does 2 + 3 equal?
2 + 3 equals what?

I probably tended toward the more colloquial, but the term equal was definitely part of the vocabulary.

SUPPLEMENT: Formulas were also routinely used on the chalkboard and on worksheets

2 + 3 = 5

When read by the students, the = sign was almost always referred to as equals not is.

Solution 2:

When I was at school (certainly at primary school) the question would be asked, "What is two plus three?", however, teaching methods have certainly changed since then. That said, the teacher/pupil may very well answer "two plus three equals five" as well as "two plus three is five"