The question asks us to find the GCF (Greatest Common Factor) of 20 and 45x. We can do this by listing the prime factorizations of each number.
20: 2 × 2 × 5
45: 3 × 3 × 5
We can see that the only common factor of the two prime factorizations is 5. Therefore, the GCF of 20 and 45x is 5. Hope this helped!