A bag had 20 coloured pencil. A few were lost. Thereafter, 8 more pencils were put into the bag. If there are 23 pencils in the bag now, find how many were lost.

Answer

To solve the problem step by step, let's break it down:

1. **Understand the Initial Situation**:
- The bag initially had 20 colored pencils.

2. **Identify Changes**:
- A few pencils were lost (let's denote the number of lost pencils as \( x \)).
- Then, 8 more pencils were added to the bag.

3. **Final Count**:
- After these changes, the bag now contains 23 pencils.

4. **Set Up the Equation**:
- The equation to represent the situation can be written as:
\[ \text{Final Count} = \text{Initial Count} - \text{Lost Pencils} + \text{Added Pencils} \]
- Plugging in the values we have:
\[ 23 = 20 - x + 8 \]

5. **Simplify the Equation**:
- Combine the numbers on the right side:
\[ 23 = 28 - x \]

6. **Rearrange the Equation**:
- To isolate \( x \), subtract 28 from both sides:
\[ 23 - 28 = -x \]
- This simplifies to:
\[ -5 = -x \]

7. **Solve for \( x \)**:
- Multiply both sides by -1 to solve for \( x \):
\[ x = 5 \]

8. **Conclusion**:
- The number of lost pencils is \( 5 \).