Let us consider the case : a discount card which will cost you $160, and then $20 per movie.
For x number of movies, Your cost is,
![160+20x](https://img.qammunity.org/2023/formulas/mathematics/college/2x0xakfxp514il71xytc8zye0c90dd2d5j.png)
Taking the second case: $40 per movie. Foe x number of movies, your cost is,
![40x](https://img.qammunity.org/2023/formulas/mathematics/college/v5gdfs8ecfsic11oi4qq7yd2pn224s318w.png)
So, when the total cost is same,
![\begin{gathered} 160+20x=40x \\ 160=40x-20x=20x \\ (160)/(20)=x \\ x=8 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/8k3emket9ultvniymjxcxhrsgbulzpctv8.png)
So after 8 movies, the total costs of the two options will be the same.