What is the greatest common factor of 54x^3, 18x, 36x^2

It's 18x because 36 and 54 are both divisible by 18, and 18 can be divisible by 18 (making 1), resulting in 18 being the most common number between the numbers, whereas the 'x' is common between all 3 numbers and since the least amount of x is 1, the answer is just x without an exponent