What are the two missing angles when you have a side of 9.9 and another side of 12.1 with an angle of 77.1

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 .

Which point on the x-axis lies on the line that passes through point c and is parallel to lino ab?

Write two subtraction equations that are equivalent to 5 + 12 = 17.