Question 998872
Hi there,
To achieve an average of 87 on
4 tests, Joe must score a total
of 87 x 4 = 348
87 + 83 + 90 = 260
348 - 260 = 88.
Joe must score at least 88 in 
his 4th test to attain an overall
average of 87 for the 4 tests.
Hope this helps :-)