Question

Mallory wants to run an average of 4 miles per day during the week (Monday
through Friday). Use the table below to find the number of miles x she needs to
run on Friday so that the mean number of miles ran per day is 4. PLEASE HELP

Answer 1

The average must be 4 miles, so:

$\dfrac{4 + 4.5 + 0 + 2.5 + x}{5} = 4$

$4 + 4.5 + 0 + 2.5 + x= 4\cdot 5$

$11 + x= 20$

$x = 20 - 11$

$x = 9$