Answer:
$3
Step-by-step explanation:
Since we know that there was $2 that she didn't use, we can subtract that from $20 to get $18 that was used (20 - 2 = 18)
We then divide 18 by 6 because she bought six pencils (18/6 = 3)
Each pencil costs $3
Hope this helps!
Edit: I saw your comment how you need to do the equation so here it is
(20 - 2)/6 = 3 (I could be wrong, but using my explanation and the information you gave, this would be correct)
