In a city , here are 25 Hindi medium schools , 18 English medium schools and 7 schools have both the medium . Find
how many schools have Hindi medium only :

Answer

To solve the problem of finding how many schools have Hindi medium only, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Given Information:**
- Total Hindi medium schools (A) = 25
- Total English medium schools (B) = 18
- Schools that have both mediums (A ∩ B) = 7

2. **Use the Formula for Union of Sets:**
We can use the formula for the union of two sets:
\[ N(A \cup B) = N(A) + N(B) - N(A \cap B) \]
Where:
- \(N(A \cup B)\) = Total number of schools (either Hindi or English or both)
- \(N(A)\) = Total Hindi medium schools
- \(N(B)\) = Total English medium schools
- \(N(A \cap B)\) = Schools with both mediums

3. **Calculate the Total Number of Schools:**
Substitute the values into the formula:
\[ N(A \cup B) = 25 + 18 - 7 \]
\[ N(A \cup B) = 36 \]

4. **Find the Number of Hindi Medium Schools Only:**
To find the number of schools that have Hindi medium only, we subtract the schools that have both mediums from the total Hindi medium schools:
\[ N(\text{Hindi only}) = N(A) - N(A \cap B) \]
Substitute the values:
\[ N(\text{Hindi only}) = 25 - 7 \]
\[ N(\text{Hindi only}) = 18 \]

5. **Conclusion:**
Therefore, the number of schools that have Hindi medium only is **18**.