If lines m and n are parallel, and ∠ 8 measures 110°, which is the measure of ∠7

I think it would be the same as angle 8 but then again i could have misunderstood the question

So  if  the sum of the enthalpies of the reactants is greater than the products, the  reaction  will be  exothermic.  if  the products side has a larger enthalpy, the  reaction  is  endothermic. you may wonder why  endothermic reactions, which soak up energy or enthalpy from the environment, even happen