Aldo's scores on four tests are 88, 85, 100, and 86. What must the score be on the fifth test for her average to be 90?

x=5th test score

(88+85+100+86+x)/5=90

(359+x)/5=90

71.8+x/5=90

-71.8              -71.8

x/5=18.2

*5       *5

x=91

the fith test score has to be 91 in order for the average to be 90

c

step-by-step explanation:

it would be see because your formula is f(x)=6x, so 6 times 1 is 6 and you go on and the best answer is c.