[HiroshiSan]

Read an introduction to proofs oriented book such as Book of Proof or my personal favorite:

https://www.amazon.ca/Mathematical-Proofs-Transition-Advance...

[FLUX-YOU]

$150+? Holy fuck.

[sn9]

Hammack's Book of Proof is freely available online and has the solutions to all odd numbered exercises: http://www.people.vcu.edu/~rhammack/BookOfProof/

[HiroshiSan]

Yeah steep price, it was a required textbook for my intro to proofs class and I don't regret the purchase...it's one I'll be coming back to often throughout my undergrad.