The question is how to put (that)you've learned into practice.你的句子应该也对 what = any thing that这里的 what 不是疑问代词词 什么而是那些 ---------------------------------你的句子翻译为 问题是你学过的怎么样能够用到实际运用当中。有了表语就没有宾语了 what you have learned 是省略了 thatthat what you have learned 作为 how 的定语
