MATH
posted by Please help!!! .
Erics 4 test grades are 85, 75, 97, 93 . What must she make on her 5th test to have an average of 87?

(85 + 75 + 97 + 93 + x)/5 = 87
350 + x = 435
x = 85 
how did you get 435?

to get rid of the denominator ( 5 ), multiply both sides of the equation by 5/
so, 5 cancels out of the left side and
5 * 87 = 435 on the right side 
Determine the values of x for which x5/3x+6 is undefined