When you simplify all of them like the square root of 36/6 it would 2.4494897.... which is a non termination decimal (so this is IRRATIONAL)
The square root of 6 is not a rational number because its a non termination decimal ----> 2.4494897.... (or you can say its like the same thing as the first one just you simplified so its IRRATIONAL)
The square root of 36/16 is RATIONAL because when you simplify you get 1.5 and you can turn that into a fraction
And finally the last one the square root of 16/6 is not a rational number because you get 1.632993...... as an answer which is IRRATIONAL
