How to equation

7.9 = 7.21+log((0.105 -4.2x)/4.2x) ? What is the value of x?

Is that

7.9 = 7.21 + log[(0.105-4.2x/4.2x)]
7.9-7.21 = log ....
0.69 = log[(0.105-4.2x)/4.2x]
4.90 = [(0.105-4.2x)/4.2x]
4.90*4.2x = 0.105-4.2x
Can you take it from here.