How is the following problem solved?

Question

What is the change of heat for bond?
NH3(g) + Cl2(g) -> N2Cl + HCl

N-H 389
Cl-Cl 243
N-Cl 201
H-Cl 431

Answer 1

add three N-H, one Cl-Cl, subtract two N-Cl, and subtract one H-Cl