Graham buys 15 pens for $12.75. What is the unit price per pen? Later, at another store, Graham finds 20 of the same pens priced at $17.40. Which offer has the lower unit price? Explain.

$12.75 divided by 15 pens = $0.85 per pen

$17.40 divided by 20 pens = $0.87 per pen

the first store has the lower price for pens. when you calculate the price of one singular pen, the first store sells them for $0.85 however the second store sells them for $0.02 more ($0.87)