The squares around the top left most 4 has 1 chance out of 3 to have a mine. All the others have one chance out of 2 or worse. If you take a chance, I'd take it there.
Edit: never mind. How did the flag above that 4 get there?
Because the two covered squares to the left of the "4-with-flag-on-top-of-it" can have only 1 mine (because of the "2" there), which means the "3" needs one more mine, which can only be on top of that "4".
I see what you mean. That means that the covered square that is top left of that 4 has 1/2 chance to be a mine. While the other two squares on its right each have 1/4 chance to have a mine in them since they require a 1/2 chance condition for it to be possible for a mine to be in either of those two remaining squares. Edit: legiblity
Sadly, it appears that only trying one of them successfully will still leave you stuck with 1/2 chance guesses so it doesn't help much still.