ok so basically it is saying substitue when a equals all of those numbers,so basically I will show you.
a (times) 2 = ? so substitute one of the numbers for a which would be like this its basically multiplication so, (-3) (times) 2 = -6 so that solves one part do the same with the other numbers and that will give you all the answers like so,
(-9) (times) 2 = -18 (-6) (times) 2 = -12 (6) (times) 2 = 12 and finally the last one is (9) (times) 2 = 18 which are all correct answers.
so basically, your answers are gonna be -6,-18,-12,12,18 which are or should be all correct
