Answer: 6.
All of the numbers in every row and column add up to 15! (Also, 6 is the only number not represented out of numbers 1 through 9.)
And to the representation to his problem you can clear,y see that 4.6 seconds is actully the the time of the whole parking. so if you just do a simple equation... 4.6x10p/2x15/10x2 would get your answer to 6
