I would solve the above question as follows :snowball14 wrote:Leonard had some 50-cent coins and 20-cent coins in the ratio of 7:4.

Each day, he took out $1 worth of 50-cent coins and replaced them with $1 worth of 20-cent coins.

After 12 days, he had an equal number of 20-cent coins and 50-cent coins in his box.

How many 50-cent coins were left in the box after 12 days?

12 x 2 = 24

12 x 5 = 60

7u - 24 = 4u + 60

3u ------- 84

1u ------- 84/3 = 28

28 x 7 - 24 = 172

Ans : 172 50-cent coins.