help i dont understand how to do this the question is "Put your answer in decimal form."

Answer:
x = 2.5
Step-by-step explanation:
Hypotenuse ² = opposite ² + adjacent ²
(x + 4)² = x² + 6²
x² + 8x + 16 = x ² + 6²
x² + 8x + 16 - x² = 6²
8x + 16 = 36
8x = 36 - 16
8x = 20
x = 20/8
x = 2.5