3' x 4.5' quilt, 24 equal squares, i need to know the side length of one square, i need to show the equation to show my work.

24 x^2 = 3*4.5 = 13.5

x^2 =13.5/24
so
x^2 = .5625 feet^2 *144 in^2/ft^2
= 81 inches^2
so 9 inches on a side