Webmath.com: Doing math with fractions

The fraction is not reduced to lowest terms. We can reduce this fraction to lowest
terms by dividing both the numerator and denominator by 5.

Why divide by 5? 5 is the Greatest Common Divisor (GCD)
or Greatest Common Factor (GCF) of the numbers 5 and 25.
So, this fraction reduced to lowest terms is

The final answer is: