Answer:
11,232,000 license plates are possible.
Explanation:
The order in which the symbols are chosen is important(ABC is a different plate than BAC), which means that the permutations formula is used to solve this question.
Permutations formula:
The number of possible permutations of x elements from a set of n elements is given by the following formula:

In this question:
3 letters from a set of 26.
3 digits from a set of 10. So

11,232,000 license plates are possible.