Okay so take:
3.99×3=11.97 that's how much the magazines cost together
add the tax which is 1.02→ 11.97+1.02=12.99
12.99 is how much the tax and magazines were now you need to add the four sheets of stickers and add the coupon because the total was more and the total was 16.49 with the coupon and without it its 17.99
take 17.99-12.99=5.00 and divide that by 4 and your answer is 1.25
EACH SHEET OF STICKERS COST 1.25 EACH