Find the y-intercept on the graph first and eliminate choices. The y-intercept is the number where the graph crosses the y-axis. There are 3 ways to find the slope:

Tilde Time
Slope Formula
Rise over Run

Once you have found the y-intercept, you can use it along with one other point from the graph to calculate the slope using the slope formula. This will allow you to eliminate any choices that do not have the correct slope.