Look at the given triangles.
a. write an expression in simplest form for the perimeter of each triangle.
b. write another expression in simplest form that shows the difference between the perimeter of the larger triangle and the smaller.
c. find the perimiter of each triangle when x=3

Perimeter:
Blue: P = 4x + 2 + 7x + 7 + 5x - 4 ⇒ 16x + 9 - 4 = 16x + 5
Red: P = x + 3 + 2x - 5 + x + 7 ⇒ 4x + 10 - 5 = 4x + 5

Difference between the perimeter:
(16x + 5) - (4x + 5) = 16x + 5 - 4x - 5 = 12x

Perimeter when x = 3
Blue : 16x + 5 ⇒ 16(3) + 5 = 48 + 5 = 53
Red: 4x + 5 ⇒ 4(3) + 5 = 12 + 5 = 17