Problem Used in Japanese Lesson

TIMSS Video Study 1999

It has been one month since Ichiro’s Mother has entered the hospital. He has decided to pray with his younger brother at a local temple every morning so that she will get better soon.

There are 18 ten-yen coins in Ichiro’s wallet and just 22 five-yen coins in the younger brother’s wallet. They have decided to take one coin from each wallet every day and put them in the offertory box and continue to pray until either wallet becomes empty.

One day, when they looked in to each other’s wallets when they were done with their prayer, the younger brother’s amount was greater than in Ichiro’s. When this happened, how many days had it been since they started their prayers?