+36 Owen had some fifty-cent and one-dolar coins. 2/7 or his coins were fify-cents coins. His mother gave him 10 one-dollar coins and five-dollars' worth of fifty-cent coins. In the end, he had twice as many one-dollar coins as fifty-cent coins. How many coins did Owen have at first?
+130037 Call the total number of coins = C
Originally, (2/7) of the coins were 50 cent coins and (5/7)were dollar coins
When his mother gives him 10 one dollar coins he has 10 + (5/7)C dollar coins
When his mother gives him 5 dollars of 50 cent coins he has 10 of them in addition to the (2/7)C worth of 50 cent coins
So
In the end, he had twice the number of one dollar coins as the number of fifty cent coins
2 [ (2/7C + 10 ] = [ 5/7C + 10] simplify
(4/7)C + 20 = (5/7)C + 10
20 -10 = (5/7)C - (4/7)C
10 = (1/7)C
70 = C = the number he had at first
