[投桃报李 / 投桃報李, tóu táo bào lǐㄊㄡˊ ㄊㄠˊ ㄅㄠˋ ㄌㄧˇ] toss a peach, get back a plum (成语 saw); to return a favor; to exchange gifts; Scratch my back, and I'll scratch yours.#67275
[mashou ; masho (ik); mahyo (ik)] (exp) (1) (pol) (ましょ is a colloquialism in standard Japanese; まひょ is a colloquialism in Kansai dialect) (See ます) (used to express the speaker's volition) I'll; (2) (used to make an invitation, request, etc.) let's; (3) (See でしょう) (used to express a conjecture) probably
[うおこころあればみずこころあり, uokokoroarebamizukokoroari] (exp) (id) (See 魚心あれば水心) if you do a favor for somebody, you will get a return favor; if a fish is friendly toward water, water will be kind to the fish too; you scratch my back and I'll scratch yours