The probability of happening of an event is `3/5`. Find the probability of not happening the event.

Explanation

To find the probability of not happening an event when the probability of the event happening is given, we can follow these steps:

### Step 1: Understand the Given Probability
We are given that the probability of the event happening, denoted as P(A), is \( \frac{3}{5} \).

### Step 2: Use the Complement Rule
The probability of the event not happening, denoted as P(A'), can be calculated using the formula:
\[ P(A') = 1 - P(A) \]
This formula states that the total probability of all possible outcomes is 1, and the probability of the event not happening is the complement of the probability of the event happening.

### Step 3: Substitute the Given Probability
Now, we substitute the value of P(A) into the formula:
\[ P(A') = 1 - \frac{3}{5} \]

### Step 4: Perform the Calculation
To perform the subtraction, we need to express 1 in terms of fifths:
\[ 1 = \frac{5}{5} \]
Now, we can substitute this into our equation:
\[ P(A') = \frac{5}{5} - \frac{3}{5} \]

### Step 5: Simplify the Expression
Now, we can subtract the fractions:
\[ P(A') = \frac{5 - 3}{5} = \frac{2}{5} \]

### Conclusion
Thus, the probability of not happening the event is:
\[ P(A') = \frac{2}{5} \]

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