Multiple. (2x- y) (3x + y)

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 .

Which inequality is equivalent to -3x < -12? x < 4 , x < -4 , x > 4, x > -4

What is the slope of the line shown below?