I am assuming a four sided figure!
p = 20 cm.
p = 2l + 2w
20 = 2l + 2w
10 = l + w
Potential values:
Area = l*w
l = 1, w = 9 A = 1*9 = 9 in.^2
l = 2, w = 8 A = 2*8 = 16 in.^2
l = 3, w = 7 A = 3*7 = 21 in.^2
l = 4, w = 6 A = 4*6 = 24 in.^2
l = 5, w = 5 A = 5*5 = 25 in.^2