you were correct throughout, but you made the slope negative in the denominator and numerator, making it positive . using what you said at first for the variables you would get the points (77,25) and (68,20).

using slope formula you get:

giving you a slope of

next i would use point slope form at first then rearrange,so..

using the point (68,20)

now to find when they are the same.to do this set y=x

so at -40 degrees they are the same