Question 890420
A + B + C = 40
A = B
C = A-5
Substitute the known values of B & C into the top equation.
A + B + C = 40
A + (A) + (A-5) = 40
3A - 5 = 40
Add 5 to each side
3A = 45
Divide each side by 3
A = 15
Sides A & B are 15 each for a total of 30
The perimeter is 40.  40-30 = 10' for side C