投桃報李 [ㄊㄡˊ ㄊㄠˊ ㄅㄠˋ ㄌㄧˇ; tou2 tao2 bao4 li3] toss a peach, get back a plum (idiom); to return a favor to exchange gifts Scratch my back, and I'll scratch yours. ◄ ►