Help me pleaseee......

Answer:
x = 6, side lengths = 36 and 18 ft
Step-by-step explanation:
If you use the Pythagorean theorem which is a squared + b squared = c squared, you get 40 squared + 6x squared + 3x squared. If you plug in 5 you get 5 × 6 = 30, and 3 × 5 = 18. So with 18 and 30, you squared them so you get 324 and 1296. Add them together and you get 1620, which is the nearest to 1600, which is 40 squared.