I've never been good at math, but this is how I think it's supposed to be solved.
Since segment SQ is half of segment OP, it wouldn't be equal; instead, it'd be multiplied by 2 to equal to OP.
Multiply segment SQ by 2.
2(5x - 2) = 8x + 6
10x - 4 = 8x + 6
Add 4 to both sides.
10x = 8x +10
Subtract 8x from both sides.
2x = 10
Divide both sides by 2.
x = 5