That depends what the value of a is.
12a + 6b + 9a + 14b =(12a + 9a) + (6b + 14b) =21a + 20b
It is: 12a+2 when simplified
-24
12a + a - 3a = 10a
12*a+8 =12a+8
13a
18
It multiplies out as: 12a-12+2 = 12a-10
17a
13a
42 = 2 * 3 * 7 12 = 2 * 2 * 3 Hence gcf (42, 12) = 2 * 3 = 6 Notice that a is also a factor of 12a and 42a. Hence gcf (42a, 12a) = 2 * 3 * a = 6a
12a + 4 - 10a = 2a + 4 or 2*(a + 2)