Plz answer if u really know it thanks so much

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 .

Is it greater than or less than7*3_9*2

Rewrite the following quadratic functions in intercept or factored form. show your work. y = 4x^2 - 19x- 5