This is a trial and error type of problem (aka "guess and check"). There are 24 combinations to try out for each problem, so it might take a while. It turns out that
g(h(k(f(15)))) = -6 f(k(g(h(8)))) = 2
So the order for part A should be: f, k, h, g The order for part B should be: h, g, k f note how I'm working from the right and moving left (working inside and moving out).
By adding all these 3 angle measures (45°, 75°, 60°) we are getting 180° in sum. And as we know that normal triangle has 180° , so that it equal only to one triangle.