The student would have to score 100% on their next test to brung their average up to 90. Here is why;
90+84+86=260
(260+?)/4=90
(260+100)/4=90
360/4=90
This is done to get the mean (or average) of a group of numbers by adding all the numbers and dividing by the amount of numbers you added together. Here it is divided by 4 because of the three tests he has taken and the test he will take.
<u><em>5 is the missing number according to the associative property is the final answer. </em></u>



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Answer:
we need a picture
Step-by-step explanation: