Please help this is make or break for my grade and I just cant seem to figure this one out

Balance the following chemical reaction. Rewrite the equation filling in the ‘coefficient’ that goes with each molecule.
a. _CO2 + _H2O  C6H12O6 + _O2

The stopwatch used by a student to measure velocity of a pulse in a slinky was of least count 0.1 second. he stops the stopwatch when a pulse has made 3 journeys from one end to the other of the slinky. he finds the seconds hand to be at 52nd division. calculate the correct time noted by him.