Joey wants to earn an A on his report card. So far he has taken 3 exams...
need to score on the last test to have an average of 90% for the 9 weeks?
To have an average of 90 for 4 exams, you know that the sum of the scores on all 4 exams would be 90 * 4 = 360. The sum of the first three scores is 88 + 92 + 84 = 264.
The last thing you have to do is 360 - 264 = 96 because then you know the score he has to get is 96 for an average of 90 on all four exams.
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