题目

（广东省汕头市苏北中学2010届高三第四次月考） I was a single parent of four small children, working at a low-paid job. Money was always tight, but we had a    21    over our head, food on the table, clothes on our backs, and if not a lot, always    22   . Not knowing we were poor, my kids just thought I was strict. I’ve always been glad about that. It was Christmas time, and although there wasn’t money for a lot of gifts, we planned to celebrate with a family party. But the big   23   for the kids was the fun of Christmas. Fortunately, I had saved 如果把分式中的x，y都扩大为原来的3倍，那么分式的值________．