名人教英文：一笔勾销 to wipe the slate clean
jorge: let me buy you a drink.
若热﹕我请你喝杯酒好吗？
ferenc: oh, thanks a lot. could i have a glass of white wine please?
费伦茨﹕啊，谢谢，我想喝杯白酒。
jorge: of course. i'll call the barman over. and i'll order a beer for myself.
若热﹕好。我叫酒保过来。我自己要杯啤酒。
ferenc: you're looking really happy today.
费伦茨﹕你今天看来十分愉快。
jorge: i've got a good reason. i've just paid back my brother all the money i owed him.
若热﹕这是有原因的。我欠兄长的钱，刚刚全部还清了。
ferenc: was it a lot of money?
费伦茨﹕欠很多钱吗？
jorge: it was. so now i don't owe him a cent. i've wiped the slate clean.
若热﹕不错。但现在我不欠他一毛钱，欠债一笔勾销。
ferenc: no wonder you're so happy.
费伦茨﹕怪不得你这么高兴。
to wipe the slate clean直译是「把石板抹干净」。slate是一种蓝灰色的石，从前常制成板状，供粉笔书写，一般用于学校。当时学生犯了过失，教师会把其名字写在石板上，处罚之后即抹去，所以，to wipe the slate clean现在引伸解作「清算旧帐」或「不咎既往」。另一相关成语是 (to start with) a clean slate，即「（以）清白的纪录（开始）」，例如﹕(1) we decided to forget our past misunderstandings and start again with a clean slate（我们决定忘却从前的误会，重新开始）。(2) the new president must be a man with a clean slate（新的总统，必须没有劣绩）。
此外，「挂帐」可说to put on the slate（记在石板上），例如﹕(1) i asked if i could put the amount on the slate, but i was refused（我问可不可以挂帐，但遭到拒绝）。(2) i forgot my wallet at home. could you put this milk on the slate?（我忘了带钱包，这牛奶可以记账吗？）
to pay back是「偿还（欠债）」，说to pay back someone或to pay someone back都是「还钱给某人」的意思。to pay back也可引伸解作「报复」或「酬答」，例如﹕(1) i will pay him back for betraying me（他出卖我，我一定会报复）。(2) thank you, joe. you have been a great help. i will pay you back（乔，谢谢你。你帮了我一个大忙，我会报答的）。to pay someone back in his own coin就是「以其人之道，还治其人之身」。