Instead of showing the formula, can you write something there in plain english as to what Value A does, what value B does and what value X does - when you enter said values?

You can still keep the formula there - for the math geeks, even though the lerp function makes it unnecessary to know the formula. At least write in plain words what those values are for.

That could be a good idea
You never ask for it, but if you (or anybody reading it) need help with this, checking the formula (I hope) it works like this:
You interpolate values of X between A (start) and B (finish). It reminds me a parametrized curve, where X would be the renowned time t
At time t=0 (X=0), you stand in A
At time t=1 (X=1), you stand in B
At 0<t<1, you stand in the straight line (because it’s linear) between A and B
Finally, at t<0 or t>1, you would be extrapolating