Alternatively you may press the "zoom +" button multiple times.
As the preview now is rather slow, I find it more comfortable to download the pic (the small icon to the right of the file name) and view it using a local viewer.
I see you want to use an implicit method to solve the system of partial differential equations. It would be better, however, to supply the equations, and all that is necessary, so that I can try to find a solution.
