First, we have to find all the factors of the number 60
So if the clues are that the number is a factor of 60 and is a prime number, the number of Juanita could be any of these numbers: 2, 3, 5. Because those 3 numbers are factors of 60 and are prime numbers.
Now let's see the first multiples of each number:
So the numbers that have 15 as a multiple are 3 and 5. So until now, the number of Juanita could be any of those two numbers let's see which of them is a factor of 20.
The number 5 is a factor of 20. That means that the number of juanita is 5 because is the only number that meets all the requirements (the clues).