Question

number 13? thanks!!!!

Answer 1

Total of the 6 lawna = 10 + 15 + 12 + 15 + 8 + 15 = $75

Given that the mean is $12 for 7 lawns,
Total of the 7 lawns = 12 x 7 = $84

Therefore the 7th lawn is:

$84 - $75 = $9

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Answer: He earns $9 on the 7th lawn. (Answer A)
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Answer 2

All you need to do is to find the number than when divided by 7 gives you 12...
7x12 = 84.
Add the current numbers. 10 + 15 + 12 + 15 + 8 + 15 = 75. 
84 - 75 = 9...
9$ the seventh time...