What is -6 divided by (-3) • (-5)

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 .

How much dextrose 70% must be mixed with dextrose 5% to prepare 1,000 ml of dextrose 20%?

If f(x)=-x^2+6x-1 and g(x)=3x^2-4x-1,find(f+g)(x)