中文： 他一脸的不以为然。 英文：也许可以这样翻译： He has disapproval written on his face. His face shows that he doesn't believe that is acceptable. His face shows disapproval. I hope I can get more better translation. Correction: I hope I can get a better translation.

he doesn't give it a damn

他一脸的不以为然 = He had a look of disapproval. 不以为然   not to accept as correct (idiom); to object / to disapprove / to take exception to http://www.mdbg.net/chindict/chindict.php?page=worddict&wdrst=0&wdqtm=0&wdqcham=1&wdqt=%E4%B8%8D%E4%BB%A5%E4%B8%BA%E7%84%B6

Good Job，iangreen，I like your answer~~

can also say: He showed a look of disapproval. ("A look" means the look on someone's face. Sometimes we say,: He gave me a funny look )