先和隔壁的借一头牛,得右:41 + 1 = 42
老大= 42 x 1/2 = 21 ,
老二= 42 x 1/3 = 14 ,
老三 = 42 x 1/7 = 6 ,
验算:21 + 14 + 6 = 41
多的那头牛再还隔壁人家