If mixing 15mL of 2.0 Molar solution of "A" with 25mL of a 2.0 Molar
solution of "B" results in a solution that is 1.0 Molar "A" and "B",
what can you conclude about the reactivity of "A" with "B"?  And why
are the concentrations half of their original?  Write an example of a
balanced chemical equation for the combination of solutions.

As a start, I'd calculate how many moles of "A" and "B" there are,
both before and after mixing the solutions.  (Hope you know how to
calculate that, given the volume and the moles-per-liter for each.)