For a composition, work from the inside to the outside. That means evaluate g(x) first, then use that result as the input of f. Here, Composition means f(g(x)). First g(2)=3(2)+5=11; then f(g(2))=-2(11)- 6=-28. This is why the final value of (f∘g) is obtained only after the second substitution, not after finding g alone.