Did you tell her anything in writing? 你跟她有过书面上的约定吗?
-No.I didn't put it in writing. 没有,我没有将它白纸黑字写下来.
tell / say / put … in writing "把...写成书面合同"
put ... down in black and write "白纸黑字写下来"(black指墨水;write指纸张)
Can you put that down in black and write? 你可以把它白纸黑字写下来吗?
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Try to translate this dialogue!

A:How soon can you deliver our order?你们什么时候能将我们订的东西送到?
B:It will take three to four weeks.We are running short on that item.需要三到四星期.我们那个货单上的现货快没了.
A:Can you promise that you will deliver by March 5,which is exactly four weeks from now?从现在起算四周后是三月五日,您能保证在这之前送达吗?
B:Yes,we can.If it's not delivered by March 5,I'll pay you $100 for each day delayed.可以.如果没在三月五日前送达.每延迟一天,我付您一百美元.
A:Great.Will you put that in writing?那好.你能将它写成书面合同吗?
B:Sure.没问题.
A:Thank you.谢谢.