HELP PLEASE it's my last one but I don't know how to do it..can somebody give me the answer and then explain how

What number should be added to both sides of the equation to complete this square? x^2-10x=7

Which of the symbols correctly relates the two numbers below check all that apply 6? 6

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