a) 1
b) -20
c) 20
d) 7

[tex]f(x)=x^2;\ g(x)=x-3\\\\(g\ \circ\ f)(x)=(x^2)-4=x^2-3\\\\\text{Put x = -2 to the equation}\\\\(g\ \circ\ f)(-2)=(-2)^2-3=4-3=1\to\boxed{a)}[/tex]