8 pencils and one eraser cost $1.35 and 6 pencils and one eraser cost $1.05. How much does one pencil cost?

$0.15 and/or 15 cents

Explanation: If you use common sense, information provided, and basic math, you notice that after 2 pencils were removed the total cost dropped 30 cents/$0.30; therefore, after 2 pencils are taken away the cost drops 30 cents and to find the price for one pencil all you have to do is divide 30/2 and you get 15 cents and/or $0.15.