1. "Did you get my envelopes?" Mateo asked his son. "I need one right away." Ignacio nodded. "Sure, Dad. Seventeen in all, and two sizes, as you said," he replied. "The big ones were one pence each more than the others, and they came to 80 pence for the lot." How many of each size did he buy?

10 large envelopes, 7 small

12 large envelopes, 5 small

13 large envelopes, 4 small