Question 800984
let sides be a, b and c
a+b+c=150 (1)
2a=b so a=b/2
c=b-20

substitute for a and c in (1)
b/2 + b + b-20 = 150
5b/2=170
b=340/5 = 68
a=68/2 = 34
c=68-20= 48

Sides are 34, 68 and 48 m

Check perimeter = 34+68+48 = 150