somebody anybody help me please

Which of the equations is the correct representation of the following word problem?

A student has two grades of 80 and 90. What grade must the student make on the next test to pass the class with a 90-grade average?


A. (80 + 90 + z)/3z = 90


B. (80 + 90 + x)/3 = 90


C. (80 + 90 + n)/3 = 100


D. (80 + 90 + 90)/3 = y