To solve this expression you need to break apart the factorial of 13 to the common prime number in the denominator, in this case the number 2. 13! can be expressed as 13 × 12 × 11 × 10 × 9 × 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1. When you break apart this factorial into its prime numbers, you are left with 13 × 11 × 7 × 52 × 35 × 210. For a fraction to result in an integer, the denominator of the fraction must share at least one prime factor with the numerator. The greatest number of 2s that can be found in the prime factorization of 13! is 10, so x ≤ 10. Eliminate (B), (C), and (E). Now for the tricky part! Any nonzero number raised to the power 0 is 1. Since the result when any integer is divided by 1 is also an integer, 0 must be included in the range of possible x values. The answer is (A).