根据题意得x≥0且x-3≠0，
解得：x≥0且x≠9．
故当x≥0且x≠9时，式子1x-3有意义．
---Now, children begin to learn English at a very early age. It is really a good thing?
---_________.
A．Yes, just in case
B．Well, it depends
C．Don’t mention it
D．Believe it or not
爸爸说：“我的年龄比小明的4倍多3。”小明说：“我今年a岁。”用含有字母的式子表示爸爸的年龄应为（ ）岁。
