The probability of the occurrence of an event is `3/10`. Find the probability of non-occurrence of the event.

Explanation

To find the probability of the non-occurrence of an event when the probability of its occurrence is given, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Probability of Occurrence**:
The probability of the occurrence of the event \( P(A) \) is given as \( \frac{3}{10} \).

2. **Use the Complement Rule**:
The probability of the non-occurrence of the event \( P(A') \) (also denoted as \( P(A^c) \) or \( P(A \text{ not occurring}) \)) can be found using the complement rule:
\[ P(A') = 1 - P(A) \]

3. **Substitute the Given Value**:
Substitute the value of \( P(A) \) into the equation:
\[ P(A') = 1 - \frac{3}{10} \]

4. **Perform the Calculation**:
To perform the calculation, convert 1 into a fraction with a denominator of 10:
\[ P(A') = \frac{10}{10} - \frac{3}{10} = \frac{10 - 3}{10} = \frac{7}{10} \]

5. **Conclusion**:
Therefore, the probability of the non-occurrence of the event is:
\[ P(A') = \frac{7}{10} \]

### Final Answer:
The probability of non-occurrence of the event is \( \frac{7}{10} \).

---