In the composition of <em>f</em><em> </em>and <em>g</em>, the equation is telling us to place the function <em>f</em> inside <em>g</em>. Observing in B that <em>f</em> is (x + 4), then this can be put in place of the x in 3x^2, making it 3(x + 4)^2 and finally the minus 5.