Bovine insulin is composed of 30 amino acids

each triplet gives a triplet of mRNA which later gives 1 amino acid..so at least an equal number of triplets must be present -->30 triplets, but let us not forget the stop codon, which doesnt give any a.a. we need at least 31 triplets--> these are encoded by 93 bases in the temp. strand.
the actual number of triplets in the gene may differ since usually , and mostly in eukaryotes, there are exons and introns in genes (introns are later removed prior to translation, and would not be translated into amino acids.) Also, there are some genes that encode for signal molecules that would direct the translocation of the protein into a specific cell compartment (such as golgi, ER...). these would also be removed and do not appear in the final product.
there are other products that may also be removed such as those that help in folding (polyA tail...)
Plus, some parts of the protein may also be later removed as part of the post-translational modifications. Best regards.

Ignoring stop and start codons, RNA splicing, and post-translational modification, a peptide of 30 amino acids is specified by 30 triplets. As a triplet is 3 bases in length, this means a minimum of 90 DNA bases (30 triplets × 3 bases per triplet) is present in the insulin gene. The actual number of triplets and bases is higher, because the gene starts and ends with start and stop sequences, some of the mRNA codons are excised prior to translation and peptide sequence, and furthermore post-translational modification of the peptide may remove additional amino acids. Thus the number of amino acids in the peptide is related to gene length but doesn’t allow precise calculation of gene length.