a piece of cake
小事一樁
解析:
a piece of cake 口語上指「小事一樁」,就像吃塊蛋糕一樣地輕鬆愉快。
練習:
A:謝謝您的幫忙。 B:小事一樁。
A:Thanks for your help. B:It was a piece of cake.