Name the angle relationship and what would the missing measurement be?

Given the graph below state whether or not the relation is a function, and give the domain and range.

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 .

Hardest math question of all time can you solve the equation. check for extraneous solutions.9∣9-8x∣ = 2x+3