a. The perimeter of a right triangle is given by summing all the sides.
4x + 2 + 7x + 7 + 5x - 4
x + 3 + 2x - 5 + x + 7
b. I think you have to combine like terms of the expressions.
16x + 5
4x + 5
c.
Large triangle: 4(3) + 2 + 7(3) + 7 + 5(3) - 4 = 12+2+21+7+15-4 = 53
Small triangle: 3 + 3 + 2(3) - 5 + 3 + 7 = 3+3+6-5+3+7 = 17