The figure shows the blueprint that a contractor uses to design ice-skating rinks. which expression gives the area of the spectator section shaded in green?

First you would want to find the area of the square and the semi circle separately then subtract the area of the semicircle from the square:
Square A=x^2
Semicircle A=[pi(x/2)^2]/2
Green area A=(x^2)-((pi(x/2)^2)/2)
Hope this helps :)