What kind problem solving questions are suitable for 1st graders

IF you want to be advanced-ish when I was in first grade we did the x2's x5's and x10's which were the most easiest for us to start with and as we developed we started doing 3's, 4's, 6's and harder ones but we stopped at 10. Also adding and Subtracting is easy.

First grade problem:-

Fact families

2 + 4 = 6

If 2 plus 4 equals 6, what does 6 minus four equal?

They should be able to use fact families to solve.