Question 921827
Let x be the equal side and y be the third side.

y = 3x-12

Perimeter = 2x + y = 48     y = 48 - 2x

Make both equations equal:

48 - 2x = 3x - 12
5x = 60
x  = 12

Sub in x to solve for y :

y = 3(12) - 12
y = 24