Because 3 divides evenly into 21 and 36 with no remainder.
The Greatest Common Factor of 12, 36, 21 is 3.
The GCF is 3.
The GCF of 21, 24, and 36 is 3.
3
The GCF is 3.
1 and 3
The GCF is 3.
The GCF is 3.
The GCF is 3.
The GCF is 3.
To simplify the fraction 21/36 you would divide the numerator and denominator by the GCF (greatest common factor) of 21 and 36 which is 3. So this simplifies to: 21/36 = (3 * 7)/(3 * 12) = 7/12.
Factors of 21: 1, 3, 7, 21Factors of 36: 1, 2, 3, 4, 6, 9, 12, 18, 36GCF (21, 36) = 3