The test scores for 8 students taking and algebra 1 test are as follows: 56, 92, 78, 64, 85, 83, 91, 77. what would the 9th student have to get on their test in order for the mean test score to be 78

X= 9th student test score

Add the 9 test scores and divide that total by 9 to equal the average.

(56 + 92 + 78 + 64 + 85 + 83 + 91 + 77 + x)/9= 78
add in parentheses

(626 + x)/9= 78
multiply both sides by 9

626 + x= 702
subtract 626 from both sides

x= 76

ANSWER: 76 is the score needed by the 9th student for a mean of 78.

Hope this helps! :)