Please help me this is the last question of my test and I need to pass!

Olivia uses the work below to determine 55% of 720 which explains the error in olivia’s solution

Find a number such that if you add 8 and divide the result by 4 you will get the same answer as if you subtracted 3 from the original number and divided by 2

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?