A piece of cake
Angela: "Can you finish your homework in ten minutes?"
Andy: "It will be a piece of cake."
安吉拉：你可以在十分钟内完成作业吗？
安 迪：小菜一碟！
Something that is very easy to do is "a piece of cake".
中文意思：小菜一碟。
A penny saved is a penny earned
Angela: "I'm going to give you $20 but I want you to put it in the bank; a penny saved is a penny earned!"
安吉拉：我会给你20美元，但是我希望你存入银行。省钱就是赚钱！
"A penny saved is a penny earned" means that little by little you will save money by not spending your money.
中文意思：省一文赚一文。