Answer:
y/x = 3/1
y = 3x
Explanation:
Drawn with the line are two slope triangles. These triangle are the same shape but not the same size. This means they are similar triangles and their side lengths form equal ratios. The ratios which they form are y/x and 3/1. This is also the slope of the line. Since they are equal, you can set them equal in a proportion.
y/x = 3/1
To solve the proportion, multiply each side by x to remove it from the denominator. This will isolate y and solve as y = 3x.