如果 3 能整除a,a又能整除12 ，那么 a=
If 3 divides a, and a also divides 12, then a =
如果两个整数a和b (a > b)都能被整数c整除，那么它们的和、差、积也能被c整除吗？为什么？
If two integers a and b (where a > b) are both divisible by an integer c, are their sum, difference, and product also divisible by c? Why?
