Factor x^2 - 7x - 18 and show work I don't know how to do it

What is the volume of this square pyramid?

When keisha installed a fence along the 200 foot perimeter of her rectangular back yard, she left an opening for a gate.in the diagram below, she used x to represent the length in feet of the gate? what is the value? a. 10 b. 20 c. 25 d. 30

Cos^2x+cos^2(120°+x)+cos^2(120°-x)i need this asap. pls me