slope is m. Parallel means it has the same slope as the line it's parallel to. Let's say the slope of line 1 is 3, and your y intercept is 12. The equation would then be y = 3x + b and b would be 12 bc x would be 0 at y intercept making the equation become y = (0)x+b and for y to be 12, b has to be 12 in this case. So y = 3x + 12
