Let's employ the first identity in logarithms.
[tex]\begin{gathered} \text{If a}^x=b \\ \text{then, x=}\log _ab \end{gathered}[/tex]Thus,
[tex]\begin{gathered} \text{If y=}\log _7x \\ \end{gathered}[/tex]Then;
[tex]x=7^y[/tex]Thus the answer is option (3)
