Four friends are sharing 1/2 of a cake. what portion of the whole cake will each friend get?

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 .

Pls! does anybody know a shortcut for answering these types of questions in the future?

Which equation represents a line that is parallel to the line whose equation is 3x-2y=7( show all work)