看不懂说中文用英文怎么说

"I can't understand" or "I don't understand" 可以用来表示看不懂的意思。

这个短语来源于英语中的"can't"和"don't"。"Can't"是"cannot"的缩写，表示不能，不会。"Don't"是"do not"的缩写，表示不要。

例句：

I can't understand this math problem. 我看不懂这道数学题。
I don't understand what you're trying to say. 我不明白你在说什么。