Answer:
x must be 6 because 6 * 3 is 18 which is greater than 16 but less than 20. x can't be 6.1 or include decimals or fractions because integers are whole numbers just adding negative numbers so therefore 6 is the only answer for this question.
Explanation:
Hope this is the answer you were looking for. If I am wrong I will try correcting my mistake. :)