To determine which of the provided numbers are irrational, let's evaluate each option:
- 169−−−√ (square root of 169): This is equal to 13, which is a rational number.
- 78−−√ (square root of 78): The square root of 78 is irrational because 78 is not a perfect square.
- 9–√ (square root of 9): This equals 3, which is a rational number.
- π (pi): Pi is an irrational number.
- 18−−√ (square root of 18): The square root of 18 is irrational because 18 is not a perfect square.
- 915: This is a whole number and hence rational.
Based on this analysis, the three irrational numbers are:
- \(\sqrt{78}\)
- \(\pi\)
- \(\sqrt{18}\)
So the correct selections are: \(\sqrt{78}\), \(\pi\), and \(\sqrt{18}\).