What is the GCF of x2 - 64?

Pls I really need help!

The pyramid below was dissected by a horizontal plane which shape describes the pyramid horizontal cross section

Answer for 10 points show work you guys in advanced < 3

Afarmer has a large field that is x feet in length. he wants to fence in a rectangular section in the middle of the field , leaving a length of 100 feet of open field behind each end of the fenced rectangle. he also wants the width of the fenced-in space to be 100 feet less than its length. find the expressions to represent the length and width of the fenced section of the field