Answer:
Each notebook cost $2.50
Explanation:
We can turn the problem into an equation
1. We have a magazine for $5, and then 4 notebooks, with the price x. They all equal to the amount $15.
5 + 4x = 15
4x = 15 - 5
4x = 10
x = 4/10
x = 2.5
2. Just to check, we can plug in 2.5 for x in the equation
5 + 4(2.5) = 15
5 + 10 = 15
15 = 15