Explanation:

- The ratio of red, blue, and green pens is given as 7:4:9.

- This is a total ratio of 7 + 4 + 9 = 20 parts.

- The total number of pens in the bag is 320.

- Each part of the ratio, therefore, represents 320 / 20 = 16 pens.

- The number of red pens, which is represented by 7 parts, is calculated as 7 * 16.

- This results in 7 * 16 = 112 red pens.

- Option 1: 112 - This is the correct number of red pens.

- Option 2: 105 - This is not correct.

- Option 3: 119 - This is not correct.

- Option 4: 126 - This is not correct.

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