Let $t(x) = 3x-8$ and $s(t(x)) = x^2 + 3x - 2$. Find $s(1)$.

Plug in x = 1: s(1) = 1^2 + 3*1 - 2 = 2.

s(1) means t(x) = 1

Since t(x) = 3x - 8, we want  3x - 8 = 1, so x = 3

Hence s(1) = 3² + 3*3 -2 = ...

Thanks for all these great answers.