Very important text:
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Keith and Lucas each had a mix of twenty-cent and one-dollar coins. Keith had 16 one-dollar coins...
(c) Keith used half of his one-dollar coins and some of his twenty-cent coins to buy a book that cost $10.40. Then, he had 7/10 of his twenty-cent coins left. How many twenty-cent coins did Keith have at first?
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1/ Keith had 16 one-dollar coins => 16 coins
2/ He spent 8 one-dollar coins and 12 twenty-cent coins to buy a book. => 12 coins
3/ After he bought a book, Keith had 7/10 of his twenty-cent coins left. => 28 coins
12 / (3/10) = x / (7/10) x = 28
Keith had 40 twenty-cent coins and 16 one=dollar coins.
Remember, all 3 boys had an equal number of coins.