正确的应该是eighty-one序数词是eighty-first ，eighty-first中文意思是第八十一

That was where he lived with Sadie Juran， his wife of eighty-one years.这是在他所住的萨迪·朱兰，他的妻子的八十一年。

Tommy Carter started working on drought-resistant soybeans in nineteen eighty-one.