Given that Gabby bought 4 pencils for $6.71 in total, this would mean that each pencil costs $1.68. On the other hand, Sydney bought 5 pens and 3 pencils with a total of $7.12. In this case, we multiply $1.68 by 3 and the total is $5.03. Now, deduct 5.03 from 7.12 and the answer is $2.09. So, $2.09 is the total amount of pens, and each pen costs $0.42. Hope this answers your question.