Answer: 13/3
Step-by-step explanation: TO turn a mixed number into an improper fraction, the best way is to multiply the denominator of the fraction by the whole number, then add the product to the numerator, then use that as the numerator of your new improper fraction, keeping the denominator the same.
>2 21/9
> 9*2 +21 =39
> 39/9
>13/3