Can someone me and explain how to solve them will give 45 points

Recall that the perimeter is the sum of all the sides.  So, for the first triangle, the perimeter is 4x+2+7x+7+5x-4 = 16x + 5 

second triangle:  x+3 + 2x-5 + x+7  (combine like terms)

Part b:  Subtract the perimeter of the smaller triangle from the perimeter of the larger triangle.

No he does not because he can only cover 12 square feet from 15 square feet which he will still need 3 more. this is because if 3×5=15 square feet and 15-12=3 which thats the answer