Firstly, we know that the notebook is cheaper than the storybook.

So in the first equation, if she buys 4 storybook 8 notebook, she have an extra of $3.20.

Second equation, if she buys 5 storybook and 7 notebook, she will be short of $11.60.

So we let X be the amount of money she has.

As we compare, we can actually find the difference in price of both item. When you take amount of money short and minus with the exceed money, you will get the difference in price.

From there, you can multiply the difference by 4 as she bought 4 notebook.

Next, take the total cost and minus off the price difference. You will get $13.20, and this is the cost of 11 item, without the price difference. So you divide it by 11 and you will get the cost of the notebook.

Once you got the cost of the notebook, you can substitute the value back into the first equation to find the cost of the storybook.