I am studying optical theory from notes given to me from a friend of a friend. Due to this some concepts are unclear. I am trying to figure out how to calculate practice problems, but their notes are not complete enough to figure out how to do them and I am unable to find the info in any book or online info. So here is a sample of the questions I am looking at.

Given info:
F1=+1.75
F2=-8.50 @ 135
F2= -12.50 @ 45
Ft=?
Your index is 1.66.


Any ideas? The section is labeled Nominal lens equation with lens maker compensation, if that helps. There are no radii, so I can't use the formula in my book. Also, the equation in the notes I have says: F(nm)=[(n'-1)F(lm)]/0.53 It has no explanation for what these stand for, but I know that n' is the index of refraction and 1 is the constant of air. 0.53 is the conversion used to compensate for different indices. Even with all this information I am at a loss. Can anyone help?