|)|-|6 (-13)| how do i find this answer?

Find the length of the following tangent segments to the circles centered at o and o' whose radii are 5 and 3 respectively and the distance between o and o' is 12. what is the tangent segment of cd?

Simplify a7/a4 a) 1/a3 b)-a/a2 c)a4/a3 d)a3

Which of the following answers is 7/9 simplified? 7/9 2/9 11/9 2/7