Evaluate the expression for the given values of the variable

x - y^3; x = - 7, y = 3

So, you know that x=-7 and y=3, and you have the expression x - y^3, and when the question says "evaluate" (in this context) it means simplify into the smallest amount of terms possible. So you substitute what x is equal to into the expression and the same for y. so you get (-7) - (3) ^3. Then you use pemdas to simplify.