Answer: x = 4
Explanation:
Focus on the horizontal pieces. The jump from 3 to 15 is "times 5".
Then focus on the diagonal pieces. The jump from 5 to 25 is also "times 5".
Therefore, the scale factor is 5 when going from small triangle to large (right to left).
For the vertical pieces 4 and 3x+8, we also have a jump of "times 5" to keep things consistent. Otherwise, the triangles wouldn't be similar.
This must mean the 3x+8 side is equal to 4*5 = 20
So,
3x+8 = 20
3x = 20-8
3x = 12
x = 12/3
x = 4
