Answer:
2 notebooks.
Explanation:
To evaluate this you just have to create an equation to solve this problem, it says that Julian has $15 in total, and he has to buy at least one notebook, so you´d have to withdraw the money of a notebook from the total, and the pens cost 4.50 each, we will be expressing the number of pens by "X" and the number of notebooks by "y" so your equation would be like this:
![4.5x+3.5y=15](https://img.qammunity.org/2020/formulas/mathematics/middle-school/wczdoavmvg1xe2d9epe6ogzx2vefuli565.png)
The number of notebooks is one, so you can put it into the equation:
![4.5x+3.5y=15](https://img.qammunity.org/2020/formulas/mathematics/middle-school/wczdoavmvg1xe2d9epe6ogzx2vefuli565.png)
![4.5x+3.5(1)=15](https://img.qammunity.org/2020/formulas/mathematics/middle-school/d1r2har62xq0n4k0bde9bqb6c5qpqbrwij.png)
Now you clear "x"
![4.5x=15-3.5](https://img.qammunity.org/2020/formulas/mathematics/middle-school/3w8jr2rr6samyw1gt27ka264t5kv0l3x4q.png)
![4.5x=11.5](https://img.qammunity.org/2020/formulas/mathematics/middle-school/n62rae5tnybfq4z4cd5trh6g79b1ovbaom.png)
![x=(11.5)/(4.5)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/vxg9t6x69yrdy0pv3wet7akg5vu0xwnaze.png)
![x=2.55](https://img.qammunity.org/2020/formulas/mathematics/middle-school/ddincs8baektokr2l0j0q1zov4tejfg0ik.png)
Since he can not buy .55 of a pen, he will only be able to buy 2 pens.