Answer:
Missing denominator = 21 :D
Step-by-step explanation:
We know that if we divide 14 by 2 we get 7.
So, if we get 7 we need to multiply it by 3 in order to get the missing denominator:
3*7 = 21
Fill in the blank to make sure it makes sense:
2/3 = 14/21
14/7 = 2
21/7 = 3