问英语math前面a还是an

用a，例如：

1. He would rap his fingers on the desk when he had difficulty working out a math problem.他做数学题遇到困难时总是要敲书桌。

2.And originally it was a math problem more or less.最初它差不多只是一个数学问题的游戏。

3. Yes, but you have a math test tomorrow.京晶：是，但你明天有一个数学测验。