the area of the shaded region can be found by subtracting the area of the inside rectangle from the outside rectangle
area of outside: 6 X 10y —> 60y
area of inside: 3 X 5x —> 15x
so the area of the shaded region is 60y-15x
the GCF is 15, so the factored form is: 15(4y-x)
