Explanation:
Adding logs of same base is equivalent to multiplying the arguments. You get:
[tex] log_{3}(35x) = 4[/tex]
Use the definition of the log to turn this into an exponential function:
[tex] {3}^{4} = 35x[/tex]
[tex]81 = 35x[/tex]
[tex]x = \frac{81}{35} [/tex]