Lunch time

In a cafeteria, 3/10 of the students are eating salads, and 3/5 are eating sandwiches. There are 30 students in the cafeteria. How many students are eating lunches other than salads or sandwiches?

Correct answer:

x =  3

Step-by-step explanation:

$$\begin{gathered} n=30 \\ S={\displaystyle \frac{3}{10}}\cdot n={\displaystyle \frac{3}{10}}\cdot 30=9 \\ A={\displaystyle \frac{3}{5}}\cdot n={\displaystyle \frac{3}{5}}\cdot 30=18 \\ x=n-S-A=30-9-18=3 \end{gathered}$$

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