2 over 3 = 11 over 8 +b

This might help you express your equations more clearly.

2/3 = 11/(8+b)

Multiply both sides by 8+b and 3.

16 + 2b = 33

Subtract 16 from both sides.

2b = 17

However, it might also be:

2/3 = 11/8 + b

Multiply both sides by 24.

16 = 33 + b

Subtract 33 from both sides.

-17 = b