Hi Keep,

These two lines intersect at (12, 4), not (4, -12).

You can find the angle each line makes with the x-axis by taking the inverse tangent of their slopes.

makes an angle of

with the x-axis.

makes an angle of

with the x-axis.

To find the angle the lines make with themselves, recognize that a triangle is formed with their intersection point and their x-intercepts. The exterior angle is 71.6 degrees. That is equal to the sum of the two remote interior angles. So the acute angle at the point of intersection of the two lines is 71.6 - 63.4 = 8.2 degrees.

Use the x-intercepts and y-intercepts and the origin to help you determine the angle each line makes with the y-axis.