单词you-scratch-my-back-and-i-ll-scratch-yours
If you give me a hand clearing the rubbish from my garden I"ll help you to paint your house - you scratch my back and I"ll scratch yours.
如果你帮助我把这些垃圾从我的花园中清除出去，我会帮助你粉刷房子-投桃报李嘛！
The contract went to a friend of the chief accountant: it"s (a case of) you scratch my back and I"ll scratch yours.
承包合同批给了总会计师的朋友，（可谓）各有好处、串通一气。
The second form is reciprocal altruism, or "you scratch my back and I"ll scratch yours" .
第二种形式是互惠的利他主义，或者说“你帮我搓背我也帮你搓背”。