Today even the friendliness of the coffee seller was a tragedy: this coffee that you ordered is drunk without milk, do you still want milk? I said yes please, she asked again how much? I said pour it in and I'll say stop. she poured drop by drop and asked 5 times: stop now? stop now? This coffee is drunk without milk....

Factors of 27: 1, 3, 9, 27

Factors of 91: 1, 7, 13, 91

When you compare the two lists of factors, you can see that the only common factor is 1. So, in this case, the GCF of 27 and 91 is 1.