9514 1404 393
Answer:
10
Explanation:
Let L and T represent the initial amounts that Leo and Theo had. Let n represent the number of bills exchanged in the first exchange. Then we have ...
L -20n +50n = T -50n +20n . . . . after the first exchange, each has the same
After the second exchange, amounts trade places:
(L +30n) +6(50) = T
Substituting this into the first equation, we get ...
L +30n = ((L +30n) +300) -30n
30n = 300
n = 10
Leo gave Theo ten $20 bills.
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Comment on the amounts
Theo started with $600 more than Leo, including exactly 16 $50 bills. Leo had at least 10 $20 bills, so he could make the initial exchange. Whatever initial amount Leo had in excess of that $200 was matched in Theo's initial amount, but Theo must have had that excess in $20 bills only. For example, Leo may have started with $300 as 10×$20 +2×$50, but Theo's initial $900 would need to be 5×$20 +16×$50.