Question 168901
Okay, first you need to factor (expand) each polynomial (group: the top of the fraction is a polynomial, and the bottom of the fraction is another polynomial).
X^2-13x+42 is the same as:
(x-6)(x-7)
x^2-36 is the same as:
(x+6)(x-6)
You can cross out both (x-6), from the top and the bottom.  Here is what is left.
(x-7)/(x+6)
That is the simplified form.  Hopefully that makes sense, and helps! :)