Sandra flips the coin 20 times. how many times can sandra expect the coin to land on tails?

What are the domain and range of the function? f(x) = -4 (sqrt)x

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 distance between (0,5) & (-4,2)