What is the sum of the liner expressions -3x + 4 and -12x -27

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 .

Pick the description of a geometric object that best matches the real world object box for a deck of card

List the sides of δrst in in ascending order (shortest to longest) if: a ∠r =x+28°, m∠s = 2x+16°, and m∠t = x+12°