1 month cost $5.
To find how many months $30 last, we can use the next proportion:
[tex]\frac{1\text{ month}}{x\text{ months}}=\frac{5\text{ \$}}{30\text{ \$}}[/tex]Solving for x,
[tex]\begin{gathered} 1\cdot30=5\cdot x \\ \frac{30}{5}=x \\ 6\text{ months }=x \end{gathered}[/tex]The certificate will last 6 months
