1) your answer for A is wrong (re-check the last step....what should be?)
2) your answer here is correct, but:
you need to be a little more precise about what a "fraction" is.
1/√2 looks like a fraction, but it isn't rational.
a number is rational if (and only if) it can be written as a fraction a/b WHERE
(and this is kind of important), b is not 0, and both a and b are INTEGERS.
so for 2), 6 is rational, because....6 = 6/1, 1 is not 0, and both 1 and 6 are integers.