Let the number of notepads be n. One magazine costs $3. Each notepad costs $3, so n notepads cost 3n. The total cost is the price of the magazine plus the price of the notepads. We add them and set the sum equal to $24.
3n + 3 = 24
Subtract 3 from both sides.
3n = 21
Divide both sides by 3.
n = 7
Answer: I bought 7 notepads.
