The combined area of two squares is 45 square centimeters . each side of one square is twice as long as a side of the other square . what is the length of each side of the larger square?

Let the side of  one square be x.    Area = x*x = x²

Then the side of other square  would be 2x ,   Area = 2x*2x = 4x²

Combined area = x² + 4x²  = 5x²

This combined area = 45 cm²

Therefore  5x²  = 45   Divide both sides by 5
                  x²  =  45/5
                  x²  = 9        Take square root of both sides
                  x   =  √9
                  x  = 3

Length of larger square is 2x  = 2*3 = 6 cm
Length of larger square = 6cm