The answers are underneath each problem. The reason this makes sense is due to the distributive property.
27. GCF of 27 and 12 is 3
3(4+9)
28. GCF of 12 and 36 is 12
12(1+3)
29. GCF of 16 and 20 is 4
4(4+5)
30. GCF of 2x and 8 is 2
2(x+4)
31. GCF of 30 and 12x is 6
6(5+2x)
32. GCF of 42x and 49 is 7
7(6x+7)
To do this, find the GCF and then divide each number by so. Then, add them in parenthisis and multiply it by the GCF