When x = 1, y= 2, z = 3, then find the value of the sum of 5x square , -2x cube y and 3y to the power 4

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 the following inequalities and show the solution on a number line. 2x+3< 3(4x+5)

Someone me i need with this stuff