Does someone know how to solve this.

If a boat travels 3 miles in 1.5 hours how far will it travel in 2 hours?

What is the slope of the line that contains the points (4,8) and (9,8)? what type of line is it?

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 .