Answer:
3
Step-by-step explanation:
for us to find the answer we have to find the number that divides evenly to both numbers with no remainder.
2: 21/2= 10.5 you can stop here because you already got an uneven answer
3: 21/3= 7 and 24/3= 8. theres your answer! 3 divides into 21 and 24 evenly with no remainder
4: 21/4= 5.25 you can stop here because you already got an uneven answer
6: 21/6= 3.5 you can stop here because you already got an uneven answer
also because i got it right on oddysseyware :D