Answer:
6 packs, 9 packs
Step-by-step explanation:
The ratio of mechanical pencil to free eraser is <em>2:4, or 1:2</em>.
So that means, for every free eraser you get, you bought the double amount of pencils.
12 free erasers x 2 = <em>24 pencils</em>
18 free erasers x 2 = <em>36 pencils</em>
And a pack of pencils contains 4.
24/4 = 6 packs
36/4 = 9 packs