I'm not sure how to do this manually but if you plug in 7/12 in a scientific calculator and then press sin -1 you'll get approximately 35.685
If you factor it, you can get an equation that is equivalent. So take out a 6. that leaves you with 6(8+3x)
10+45+16
The answer would be 71
the answer is 
subtract 6x on both sides → 
divide both sides by -2y → 