What is the image point of (-1,-6) after the transformation R2700 D3?

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 .

What is the number 321,000,000 in scientific notation? also what is the number? ?

15/16 as a decimal rounded to the nearest hundredth