If $f(x) = 3x^2 - 5$, what is the value of $f(f(-1))$?
f(-1) = 3 (-1)^2 - 5 = 3 - 5 = -2
So
f (f (-1) ) = f (-2) = 3 (-2)^2 - 5 = 12 - 5 = 7