How do I figure out this mixed number problem?

You answer is correct except there is an improper fraction. You got 12 parts of 8. You need only 8 to make 1 whole No. So, 12 parts minus 8 leaves you with 4 parts so the balance is 4/8 but this can be further improve to 2/4 and again to 1/2. So the final answer is 21 1/2.