new perimeter is 4040-2424= 1616
original, let x and y be length and width
2x + 2y = 4040
new
2x/2 +2y/3 = 1616
x +2y/3 = 1616
x = 1616 - 2y/3
sub this x value into first eq
2(1616-2y/3) + 2y = 4040
3232 - 4y/3 + 2 = 4040
put like terms together
-4y/3+2y=4040-3232
2y/3=808
multiply both sides by 3
2y = 2424
divide both sides by 2
y=1212
sub this y value into any eq. i chose eq 1
2x+2(1212)= 4040
2x = 4040 - 2(1212)
2x = 1616
x = 808
so the length is 808 and the width is 1212