The perimeter is all of the sides added together.
Side + side + side = P
Plug in the side values and perimeter
(X+ 4) + 10(x-1) + 4x = 288
X+ 4 + 10x - 10 + 4x = 288 Simplify
15x - 6 = 288 Combine terms
15x = 294
x = 294/15 or 98/5
Rectangle is the same
Side + side + side + side = 2600
(X+3) + (X+3) + (2x-6) + (2x-6)
6x - 6 = 2600 Combine like terms
6x = 2606
x = 2606/6 or 1303/3
