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Let's analyze the questions and solve them:

### Question 21:
John answered \( \frac{7}{8} \) of the 40 questions correctly. We need to find how many items he answered incorrectly.

- Total questions = 40
- Correct answers = \( \frac{7}{8} \times 40 = 35 \) (since \( \frac{7}{8} \times 40 = \frac{280}{8} = 35 \))
- Incorrect answers = \( 40 - 35 = 5 \)

Thus, John answered **5** items incorrectly. The answer to question 21 is **A. 5**.

### Question 22:
Which procedure can be used to find how many items John answered incorrectly? Let's analyze each statement:

- **I.** Subtract \( \frac{7}{8} \) from 1 and multiply the difference by 40.
  - \( 1 - \frac{7}{8} = \frac{1}{8} \), and \( \frac{1}{8} \times 40 = 5 \) (Correct method).

- **II.** Subtract \( \frac{7}{8} \) from 1 and divide the difference by 40.
  - \( \frac{1}{8} \div 40 \) does not give the correct result (Incorrect method).

- **III.** Multiply 40 by \( \frac{7}{8} \) and subtract the product from 40.
  - \( 40 \times \frac{7}{8} = 35 \), and \( 40 - 35 = 5 \) (Correct method).

- **IV.** Multiply 40 by \( \frac{7}{8} \) and subtract the product from 40.
  - This is the same as statement III and is also correct.

The correct options are **I and III**, so the answer to question 22 is **B. I and III**.

### Question 23:
The friends ordered two pizzas. One had 8 slices, and the other had 6 slices. They ate 3 slices from the first pizza and 2 slices from the second pizza. We need to determine how much pizza is left.

- First pizza: 8 slices in total, 3 slices eaten, so 5 slices left.
- Second pizza: 6 slices in total, 2 slices eaten, so 4 slices left.

The total pizza left can be expressed as:
\[
\text{Remaining pizza} = \frac{5}{8} + \frac{4}{6}
\]

Converting both fractions to have a common denominator:
\[
\frac{4}{6} = \frac{16}{24}, \quad \frac{5}{8} = \frac{15}{24}
\]
Adding them together:
\[
\frac{15}{24} + \frac{16}{24} = \frac{31}{24} = 1\frac{7}{24}
\]

So, the amount of pizza left is **1 and \( \frac{7}{24} \)**, which is option **B. 1 \( \frac{7}{24} \)**.

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Would you like more details on any of these solutions?

Here are 5 related questions for further practice:
1. If John answered \( \frac{5}{6} \) of the 40 items correctly, how many did he get wrong?
2. How would you calculate the number of correct items if John had answered \( \frac{3}{4} \) of the test correctly?
3. What fraction of a pizza is left if 3 slices are eaten from a pizza with 12 slices?
4. How many questions did John answer incorrectly if he answered \( \frac{4}{5} \) of the 50-item test correctly?
5. Can you devise a formula to find the number of incorrect answers if the correct fraction and total number of items are given?

**Tip:** When adding or subtracting fractions, always find the least common denominator (LCD) for easier calculations.

In a 40-item Mathematics summative test, John answered 7/8 of the items correctly. How many items did he answer incorrectly? What procedure would you use to find the number of items John answered incorrectly?

Learn how to calculate the number of incorrect answers in a 40-item test where 7/8 of the items are answered correctly. This solution walks through basic fraction operations and proportions, suitable for students in Grades 6-7.

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