Answer: 410 centimeters
Explanation:
1. You know that she put 18 hangers on the wall at 20 centimeters intervals, therefore, the number of spaces is:
![spaces=n-1](https://img.qammunity.org/2020/formulas/mathematics/middle-school/xdlo4nhhgkvrh2sx4e2vxoi2agdt1bcgzf.png)
Where n is the number of hangers put on the wall.
2. Then, you have that the number of spaces is:
![spaces=18-1=17](https://img.qammunity.org/2020/formulas/mathematics/middle-school/m14qe4zlhlq4i3occsj938vug9b3xbbma9.png)
3. So, the width of Leslie's room can be calculated as following:
![width=(2*35cm)+(17*20cm)\\width=410cm](https://img.qammunity.org/2020/formulas/mathematics/middle-school/h3tn2idetrwbg09ylfwxgivlvm623qes0z.png)