Final answer:
After writing 15 thank-you notes on Saturday and another 15 on Sunday from the original 48, Cam has 18 thank-you notes left to write.
Step-by-step explanation:
The question asks us to calculate how many thank-you notes Cam still has to write after completing some of them over the weekend. Initially, Cam has 48 thank-you notes to write.
On Saturday, he writes 15 of them, which leaves him with 48 - 15 = 33 thank-you notes. Then, on Sunday, he writes another 15 notes, reducing the number of unwritten thank-you notes to 33 - 15 = 18 thank-you notes. So after Sunday, Cam still has to write 18 thank-you notes.