Answer:

Step-by-step explanation:
Given

To express as a rational number with 91 on the denominator.
91 ÷ 7 = 13
Thus multiply the numerator and denominator by 13, that is
= 
-4*3 1/4 would be and expression you can use
Answer:
12/13
Step-by-step explanation:
We know that cosine is the adjacent side divided by the hypotenuse in a right triangle.
The adjacent side to angle C is BC
The hypotenuse is AC because it is opposite to the right angle
So...
cosine is (BC)/(AC)
36/39
12/13