The GCF of 21, 77, and 84 is 7. First you have to find the lowest common factor, that is able to be divided by all the numbers. E.g. 7 *21/7=3 *77/7=11 *84/7=12 3 and 11 are prime numbers and can therefore not be any divided further. Therefore the answer is 7.
38.5
12.8333
77
0.8851
15.4
0.8182
77
77
0.0349
77
77