Step-by-step explanation:
[tex]2x + y + 3x - 7y \\ = (2x + 3x) + (y - 7y) \\ = (5x) + ( - 6y) \\ = 5x - 6y \\ = mx + b \\ where \: \: m = 5 \\ where \: \: b = - 6y[/tex]