Use Kirchoff's equation to solve this question.

(delatH2-deltaH1)/(T2-T1) = deltaCp of reaction

Since equation is A+B--->C

deltaCp of reaction = Cp of C - Cp of A - Cp of B

                              = 3x - 2x - x (as the ratio is C:B:A = 3:2:1)

                              = 0

put this in Kirchoff equation

So delta H2 = delta H1