What is the value of $a + b + s + t$

Question

I'm confused as to how to approach this. I've tried to foil it out.

$$x^3(3x-1)=a+bx+sx^2+tx^3$$ The equation above is true for all values of $x$, where $a$, $b$, $s$, and $t$ are constants. What is the value of $a+b+s+t$?

Answer 1

hint: let $x = 1$ in the equation.