Answer 1

The three sets of Pythagorean triplets such that each set has numbers less than 30 are 3, 4 and 5; 6, 8 and 10; 5, 12 and 13
Proof:
In 3, 4 and 5
3² + 4² = 5²
⇒ 9 + 16 = 25
⇒ 25 = 25
In 6, 8 and 10
6² + 8² = 10²
⇒ 36 + 64 = 100
⇒ 100 = 100
In 5, 12, and 13
5² + 12² = 13²
⇒ 25 + 144 = 169
⇒ 169 = 169