Use technology to find points and then graph the line y = 5/3x – 1

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 .

The sum of two numbers is 12 and their difference is 18 what are the two numbers

Find the y-intercept and x-intercept for the equation 5x-3y=60 what is the y-intercept