Final answer:
Irrational numbers cannot be expressed as simple fractions. From the given options, only \(\sqrt{26}\) and \(\sqrt{761}\) are irrational because their square roots are not integers.
Step-by-step explanation:
An irrational number is a number that cannot be expressed as a simple fraction - it's decimal goes on forever without repeating. A rational number can be written as a fraction a/b, where 'a' and 'b' are integers, and 'b' is not zero.
To comprehend which numbers are irrational from the list given, we must understand that if a square root of a number results in an integer, it is rational. If it does not result in an integer, it is irrational. Here, \(\sqrt{169}\) is rational because it equals 13, which is an integer. However, \(\sqrt{26}\), \(\sqrt{761}\), and \(\sqrt{81}\) are irrational because their square roots do not result in integers, and cannot be expressed as a simple fraction (\(\sqrt{81}\) actually equals 9, which is an integer, thus it is a typo in the question).