for this case we need to identify which number is a rational number and we need to remember that a rational number is any number that can be obtained from two integers :
[tex]\sqrt{81}=9=\frac{81}{9}=9\text{ (rational number)}[/tex][tex]\sqrt{50}=\sqrt{4\cdot5}=2\sqrt{5}\text{ (not rational number)}[/tex]
this number is not rational because icannot be obtained from the division of two integers
[tex]-12=\frac{-24}{2}=-12\text{ (rational number)}[/tex][tex]0=\frac{0}{10}=\text{ 0 (rational number)}[/tex][tex]6.54545454\text{ (not a rational number)}[/tex]
The reason is because we can't obtain the number with two integers
