First simplify like terms (things with the same letter):
3g + 7g + 8 = -10 + g
10g + 8 = -10 + g
Next we should take g off both sides:
9g + 8 = -10
Next isolate 9g by taking 8 off both sides:
9g = -18
Next divide both sides by 9 to find the value of g:
g = -2
