What are all the common factors of 15 ,45, 90

The common factors are: 1, 3, 5, 15
GCF (greatest common factor): 15
15                     45                                  90
^1, 3, 5, 15         ^1, 3, 5, 9, 15, 45,         ^1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90,

1.17+3.99a. you combine the terms with a to create 3.99 and the 1.17 stays because it has no like terms or a variable

The answers are 20,30,80,180,960,890,1230,4560. on the first row