First one: Irrational numbers are any numbers that go on forever in the decimal without ever repeating. Any square roots of numbers that aren't perfectly square, such as 4 and 9, are irrational. And anything with pi, or , is always irrational.
Second one: 144 and 100 are perfect squares, meaning it can be created by multiplying the same number by itself, in this case 12 and 10. Subtract those and you get 2.