Which is true regarding the graphed function f(x)? the graph is attached and the choices?

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 .

How do you solving the solution of each system using elimination?

Joe has some money in his bank account he deposits 45$ write an expression that represents the amount of money in joe's account