Question 1204991
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A quick informal solution using logical reasoning, if formal algebra is not required.<br>
The 19 scores she has are, on average, 87-85 = 2 points short of the desired mean; so together they are 19*2 = 38 points short.  That means the missing score must be 38 points above the desired mean.<br>
ANSWER: 87+38 = 125<br>