Since we are adding 21 1/4 to 6 2/7, we need to find the LCD, or, least common denominator, so that we can add 1/4 and 2/7 together.
1*4=4 1*7=7
2*4=8 2*7=14
3*4=12 3*7=21
4*4=16 <u>4*7=28</u>
5*4=20
6*4=24
<u>7*4=28</u>
Since we had to multiply 7 four times to get it equal to 28, we need to take 2/7 * 4/4. This will give you 8/28. Then, since we multiplied 4 seven times to get it equal to 28, we need to take 1/4 *7/7. This will give you 7/28. Finally, you need to add 8/28 and 7/28 since they now share the same denominator.
8/28 + 7/28=15/28
For our last step, we need to add the whole numbers together so the answer is complete.
