Hey guys, I need help with this algebra assignment. Any answers will help! I’d be happy to give you brainliest for whoever helps me. Also please show your work, Problems are in the pictures :)

What is the domain of the function f(x)=^9x

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 .

Find the slope and the y-intercept if there's one and the equation of the line given these two points( 3, 2) and( 3, -4)