Size of Gap Fill box

I made a gap fill page, which I want students to fill in on mobile. The gap fill exercise requires students to fill in a formula, so the placement of the gapboxes is quite important. On mobile, the placement of these boxes is all screwed up.

Is there a way for me to reduce the width of gap-fill boxes manually so that their placement won't mess up on most mobile screens?

Or is there a way to use gap-fill in the math option (with LaTeX)? Because when I try to use that, it seems to mess up the formula.