Answer:
10
Explanation:
Very easy equation if you know how to do it. All you need to do is divide your total amount of something (in this case "150" as that's our amount of "money we're given") by whatever the price or amount is. (In this case 15. Each cartridge costs $15. I'm not amazing at explaining things like this.. Sorry about that. If you have any questions about this feel free to let me know!)
So to put it "all together":
150 ÷ 15 = 10.
10 is your answer.
Hope this helps and have a nice day!