I'm sorry having to tell you, but 90.5 is the correct answer. I have no idea how you guys do these calculations, but I have always found it easiest to treat them just as equations and add the sum up the enthalpies of formation... anyway, you get the result by adding -212.6 (twice enthalpy of formation for C2H5Br) + 104.4 (C2H4) minus 72.8 (HBr). Then divide by two as the unit is 'per mol'- as your chemical equation for the formation of C2H5Br has 2 as a coefficient before C2H5Br.
Hope that helps...