Now put common variables on both sides (one side with x's and other side without)
x log (3) - x log (5) = log (7) - log (4)
Now work out the log's. Either use log or ln (logaritmus naturalus)
I'll use both ways, first log: (which is standard log10)
0.477121x - 0.69897x = 0.84509 - 0.60205
-0.22184x = 0.24303
Now divide by -0.22184
x = -1.09555
The ln way: (which is log of e)
1.09861x - 1.60943x = 1.94591 - 1.38629
-0.510825x = 0.559615