Use distribution property first
5(b - 4) - 3b = -6
5b - 20 - 3b = -6
Then simplify terms that has same variable
5b - 20 - 3b = -6
5b - 3b - 20 = -6
2b - 20 = -6
Simplify the constants
2b - 20 = -6
2b = -6 + 20
2b = 14
You find b
2b = 14
b = 14/2
b = 7
The answer is 7
