PLEASE HELP FAST *I need the legs not the angle*

What is the measure of ac? 5 units 13 units 26 units 39 units 3x- 2b 6x + 9

Suppose you are an avid reader and are looking to save money on the cost of books instead of paying about $20 for each book, you decide to look into purchasing a kindle for $120 you can purchase e-books for about $5 each 1. find the slope-intercept equation for the cost of the hard copy of books using x to represent the number of books 2. find the slope-intercept equation for the cost of the kindle with cost of e-books using x to represent the number of books

What is the axis of symmetry of the function f(x)=-(x+ 9)(x-21)