Question 1008387
Perimeter P = 2L + 2W = 80.  We also have
2W = L + 5  or 
L = 2W - 5
Now substitute this onto the first equation...we get
2(2W - 5) + 2W = 80
4W - 10 + 2W = 80
6W - 10 = 80
6W = 90
W = 15 cm
L = 2(15) - 2 = 25 cm