Answer:
Her first exam score was a 78, her second exam score was a 89, and his third exam score was a 94.
Step-by-step explanation:
Use the formula for the mean: sum of elements / number of elements
Let x represent her first exam score.
Her second exam score can be represented by x + 11, since it was 11 points better than her first.
Her third exam score can be represented by (x + 11) + 5, since it was 5 points better than her second.
Plug in all of these expressions into the mean formula. Plug in 87 as the mean, and plug in 3 as the number of elements (since there are 3 scores):
mean = sum of elements / number of elements
87 = ( (x) + (x + 11) + (x + 11) + 5 ) / 3
Add like terms and solve for x:
87 = (3x + 27) / 3
261 = 3x + 27
234 = 3x
78 = x
So, her first score was a 78.
Find her second score by adding 11 to this:
78 + 11 = 89
Find her third score by adding 5 to the second score:
89 + 5 = 94
Her first exam score was a 78, her second exam score was a 89, and his third exam score was a 94.
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