Hey there! :) 
-g + 2(3 + g) = -4(g + 1) 
Simplify.
-g + 6 + 2g = -4g - 4
Add like terms. 
(-g + 2g) + 6 = -4g - 4
Simplify. 
g + 6 = -4g - 4 
Add 4g to both sides & subtract 6 from both sides to isolate "g."
g + 4g + 6 - 6 = -4g + 4g - 4 - 6
Simplify. 
5g = -10 
Divide both sides by 5. 
5g/5 = -10/5
Simplify.
g = -2
Hope this helped! :)