The answer is 30 days.
The solution for this is to find the least common multiple. By getting the multiple of both numbers.
Multiples of 2: 2,4,6,8,10,12,14,16,18,20,22,24,26,28,30,32,34,36,38,40…..
Multiples of 15: 15,30,45,60,75……..
The Least Common Multiples of 2 and 15 is 30. So, Inez will do them both again in 30 days.
The least common multiple (LCM) of two numbers is the smallest number that is multiple by the both number.