Hi There!
Answer:
20
Explanation:
To find a common denominator you need to find a number that both denominators you start with equally go into the denominator.
A trick that my teacher taught me was to multiply both denominators together to get the common denominator.
5 * 4 = 20
So now we know that the common denominator is 20.
Then what you multiplied to get that numbered you want to do to the numerator as well.
Hope This Helps :)