Help me out, please :-)

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 .

(urgent ) use pi 3.14 to estimate the circumference of the circle to the nearest hundredth middle is 4in (urgent )

In july, the average temperature in one us city was 29°c. by december, the average temperature had fallen by 29°c. explain why the average temperature in december was 0°c.