# Proving a language is regular [duplicate]

I am asked to find

Prove that the following languages are regular languages:

(a) $$\{a^nb^ma^k \mid n\geq3,m\geq1,k\geq1\}$$

(b) $$\{a^n \mid n\neq3 \text{ and } n\not\equiv2 \mod7\}$$

(c) $$\{a^nb \mid n\geq2\}\cup\{ab^m \mid m≥3\}$$

I have a vague understanding of pumping lemma, and how to prove a language is not regular, but was hoping that someone could walk through (a) with me to give me a better understanding and allow me to do the rest on my own.