Answer: The required value of the given expression is 3.
Step-by-step explanation: We are given to evaluate the following logarithmic expression :

We will be using the following logarithmic properties :

From (i), we get
![E\\\\=\log_7343\\\\=\log_77^3\\\\=3\log_77~~~~~~~~~~~~~~~~~~~~~~~~~~~~[\textup{Using property (i)}]\\\\=3*1~~~~~~~~~~~~~~~~~~~~~~~~~~~~[\textup{Using property (ii)}]\\\\=3.](https://img.qammunity.org/2017/formulas/mathematics/high-school/owctorpp2dgs7zl6b3q580fos5gvd7vsfs.png)
Thus, the required value of the given expression is 3.