To factor the expression:

We can follow the next steps:
1. We can see that 30 and 12 can be divided by 2, so we have 2 as a common factor:

2. We also can see that 15 and 6 can be divided by 3, so 3 is another common factor for this expression:

Now, we can see that 5 and 2 are prime factors, and we cannot find any other factor. Therefore, the expression 30 - 12x can be factored as:

Thus, the expression can be factored as 6(5 - 2x).