For 25 points

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

A student's grades are 92, 73, 87, and 91. What is the average of the student's grades?


(92 + 73 + 87)/3 = x


4(92 + 73 + 87 + 91) = x


(92 + 73 + 87 + 91)/4 = x


(92 + 73 + 87 + 91)/5 = x