Question 712360
to achieve a mean score of 85 over 5 tests then the total score for those 5 tests must be 85*5 = 425
the total score so far, over 4 tests, is 72 + 76 + 90 + 90 = 328
so the difference between these two numbers is the score needed in the 5th  and final test
425 - 328 = 98
so 98 marks are required.