When simplifying fractions we need to reduce both the numerator (the number on the top of the fraction) and the denominator (the number on the bottom of the fraction) so that both numbers have no common factors (numbers that can be evenly divided into both)
Let's take this the example
30/100
We need to find the greatest common factor of 30 and 50 and then divide both numbers by the greatest common factor. Let's list all of the numbers that go into 30 and 100
2, 5, 10
10 is the greatest common factor. Divide both 30 and 100 by 10 to get the simplified fraction
3/5
This is the simplified form.