Can anyone help me solve this? Find the slope of a line between the points (3, 5) and (-3, -2)?

If you imagine these are two points on a right-angled triangle. That means the third point, where the right angle is, is at (3, -2). If you look at this diagram:

A = (-3, -2)
B = (3, 5)
C = (3, -2)

What you want is the angle at point A. The tangent of that angle is the length of the opposite over the adjacent. The opposite is B-C (7) and the adjacent is C-A (6). Therefore the tangent of your angle is 7/6. The angle itself is the arctangent of 7/6, which is 49.4°.