Simplify each expression. if not possible, write simplified.

1. 12a - a

2. 3x + 6x

3. 3x - 1

1).  You have 12 of something, and 1 of the same thing is taken away.
How many of it do you have then ?

2).  You have 3 of something, and 6 more come along.
How many of it do you have then ?

3).  Simplified.