You divide it with valid numbers that can be dividable with both numerator and denominator.
15/40 can be divided by 5 to make it into the simplest form
= 3/8 , now we can no longer divide it, so its the simplest form
Explanation:
15 : 40
Both have table of 5 in common
5 : 8
5.2m questions
6.8m answers