Can someone help me find the value of x

Answer: 4
Step-by-step explanation:
Use the triangle to the right to find the measure of the side the two triangles share. That side is 8.06 roughly and squared it’s 65. I used the 65 to solve for b in a^2 + b^2 = c^2
65 + b^2 = 81
b^2 = 16
b = 4