Verified answer

You need information that you haven't provided in the question. Perhaps your text has a table of ΔGof for these compounds. In that case,

ΔGorxn = Sum of ΔGof products - ΔGof reactants

Just plug in the values that you find and calculate the free energy change of the reaction.

ΔG = ΔG formation of products - ΔG formation of reactants

ΔG = ΔG∘f [ NH4Br(s) ] - [ ΔG∘f (NH3(g) + ΔG∘F (HBr(g) ]

Plug in the values ( check back of your textbook for ΔG∘formation values

CH4(g)+3Cl2(g)→CHCl3(g)+3HCl(g)

ΔG = [ΔGf (CHCl3(g)) + 3 x ΔGf (HCl(g) ] - [ ΔGf (CH4(g) + 3x ΔGf (CL2(g)) ]