(2 + (7 - 10)) -> (2 + -3) -> -1 f(x) = (x - x) (4 + f(5)) -> f(x) = (x - x) (4 + (5 - 5)) -> f(x) = (x - x) (4 + 0) -> f(x) = (x - x) 4 h(z) = (g(z) - z) g(y) = (y + 1) h(17) -> h(z) = (g(z) - z) g(y) = (y + 1) (g(17) - 17) -> h(z) = (g(z) - z) g(y) = (y + 1) ((17 + 1) - 17) -> h(z) = (g(z) - z) g(y) = (y + 1) (18 - 17) -> h(z) = (g(z) - z) g(y) = (y + 1) 1 4 in ----------- 4 in ----------- 4 in 1 in 2 in ----------- ----------- 1 in 2 in --------------------------- (1 + 2) in 1 + 2 is not in f(x) = x g = f f(x) is not in x in y in 1 in 1 in ----------- ----------- ----------- ----------- f in x in x in g in z in y in 1 in 1 in ----------------------------------- ----------------------------------- ------------------------- f(x) = x in g(z) = y in (1 - 1) in ------------------------------------------------------------------------------------------------------------- f(x) = x g(z) = y (1 - 1) in f(x) = 1 f(1) g(x) = 2 g(2 + 2) is not in