Answer:
126
Explanation:
You want to know the score needed on your 3rd game for an average of 125, given the first two scores were 134 and 115.
Relative
The given scores relative to the desired average are 134 -125 = +9, and 115 -125 = -10.
The sum of these is 9 -10 = -1. To obtain your average you need a score that is different from 125 by the opposite of this amount:
125 -(-1) = 126
You need a score of 126 on your third game.
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Additional comment
Often, it is easier to answer questions like this by considering the differences from the desired average. The final total difference from average must be zero.
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