It cost a bike manufacturer $80 to make a bike. Mike buys a bike from the manufacturer for $128. find the percent increase

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 .

Solve for x, y, and z. show all steps.

What is the celsius temperature that is equal to 94 degrees fahrenheit using the formula f=9/5 c+32