Because we are looking for an estimate, we can round 168 people to 170. Then, 2 pins for about 170 people would be 340 pins (simply multiple 170 x 2). Then we can round 9 cents to 10 cents, or .1 dollars. 340 pins times .1 is just 34 dollars (move the decimal once to the left).
Answer: About 34 dollars
