Rewrite each exponent in standard form

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 .

I'll give brainliest if you answer right : )

Bobby bought 1.12 pounds of turkey at a cost of 2.50 per pound. carla bought 1.4 pounds of turkey at a cost of 2.20 per pound. who spent more and by much?