x^3 + y^(-2)
to evaluate means you substitute the value of x and y which are given in the problem.
first, recall some laws of exponents. if a term is raised by a negative number, it is also equal to its reciprocal raised to the that number but positive in sign. for example,
5^(-3) = (1/5)^3
thus we can actually rewrite this equation as
x^3 + (1/y)^2
substituting x = -3 and y = 4,
(-3)^3 + (1/4)^2
(-3)*(-3)*(-3) + (1/4)*(1/4)
-27 + 1/16
-26 15/16
hope this helps~ :)