Question 661521
p = x + y + z = 45
x = longest  
y = second = 1/2x
z = third =  x - 10
Substituting into perimeter
x + (1/2x) + (x-10) = 45
combine like terms
2x + 1/2x - 10 = 45
2.5x = 55
x = 22 ft
y = (1/2)22 = 11 ft
z = 22 - 10 = 12 ft
Proof
22 + 11 + 12 = 45