Explain in your words the process to factorise a difference of perfect squares.

In two fractions have the same denominator but different numerators, which fraction is greater? give an example

Iam trying to solve a linear equation for the shoe size of someone 84" tall taking into consideration example 1 is 69" tall with a shoe size of 9 and example 2 is 72 inches tall with a shoe size of 11. i understand that the equation should be y=mx+b and that on the graph the answer is (3,2) but i just don't understand how to create the equation to solve for 84-inches and 60-inches tall questions. after two days, i need .

5,600 x 10^3 = a) 560 b) 5,000,600 c) 5,600,000 d) 56,000