Answer:
see explanation
Step-by-step explanation:
The perimeter (P) is the length of all 3 sides of the triangle
The triangle is isosceles with 2 equal sides 20 - 7xy
P = 20 - 7xy + 20 - 7xy + 12 = 52 - 14xy
When x = 2, y = 1, then
P = 52 - 14(2)(1) = 52 - 28 = 24
