Answer:
12 students
Explanation:
Given
![Students = 54](https://img.qammunity.org/2021/formulas/mathematics/college/gvt42j006sylhn8k823f47tx521e8kkt5j.png)
Required
Determine the number of students that eat lunch once a week
In Sets;
If out of 9, at least 7 eats one a week then
9 - 7 eats lunch once a week
![9 - 7 = 2](https://img.qammunity.org/2021/formulas/mathematics/college/xj2gkworzh5c1ia3o22u4medhs7kbmwqms.png)
In other words;
2 out of 9 students eat lunch once a week
Number of students in this category is then calculated as thus;
![Number = (2)/(9) * 54](https://img.qammunity.org/2021/formulas/mathematics/college/7azdqyb7i1w4xfc37gwhtpo08zwsrgvbxd.png)
![Number = (2 * 54)/(9)](https://img.qammunity.org/2021/formulas/mathematics/college/5gfzxahcciskb1z3t8dznca6chn0ou2cma.png)
![Number = (108)/(9)](https://img.qammunity.org/2021/formulas/mathematics/college/b8jcxohztfkwk1qdyjhkfkmuorg1uynwrv.png)
![Number = 12](https://img.qammunity.org/2021/formulas/mathematics/college/ly5k0vtdvbm2p01zvdv0wv5htfxofylyfp.png)