Question 895505
Simple! Think he should earn 'X' marks. Mean is the total marks divided by number of exams.

All together .. there are 5 exams.. 

{{{(92 + 85 + 90 + 92 + X)/5 = 90}}}

{{{(359 + X)/5 = 90}}}

{{{X = 450-359}}}

{{{X = 91}}}