Question 9
Barbara writes numbers consisting of four digits: 3, 5, 7 and 9, according to the following rules:
- Digit 7 does not appear in the first nor the last positions.
- Digit 7 should be to the right of the digit 5. (For example, digit 5 in the number 7395 appears to the right of digits 7, 3 and 9.)
Find all such possible numbers.
- Digit 7 does not appear in the first nor the last positions.
- Digit 7 should be to the right of the digit 5. (For example, digit 5 in the number 7395 appears to the right of digits 7, 3 and 9.)
Find all such possible numbers.