y = 4x -3
Find the y-intercept; (0, -3). Plug this coordinate's y-value in for the b (y = mx + b).
Now, find two points on the line to do slope formula, or you can do rise over run. For example, if I had the points (0, -3), and (1, 1), I'd have the formula [1 - (-3)] / (1 - 0), in which the division sign represents a fraction. The simplified version of this fraction will be 4.
Plug this value in for m.
Now, your equation is y = 4x - 3