不会做用英文怎么说

不会做 can be expressed as "don't know how to do" or "can't do" in Engpsh.

例句：

I don't know how to do this math problem. (我不会做这道数学题。)
I can't do this task. Can you help me? (我不会做这个任务，你能帮帮我吗？)

来源：这个说法是直译自中文，没有特殊的来源。