Jack received 4 emails and sent 13 letters in the morning. He then received 2 emails and sent 17 letters in the afternoon. How many emails did Jack receive in the day?
In the morning, Jack received 4 emails and sent 13 letters. 
In the afternoon, Jack received 2 more emails, for a total of 6 emails. He also sent 17 letters. 

Therefore, Jack received 6 emails in the day.