Adding a negative number is the same as subtracting a positive number. So 2315.5 - 3166.75 = -851.25
The first answer is B because the bottom half of the proportions are how many km/minutes he CAN run, while the top half of the proportion is how many he WILL run.
He will run 60km in 285 minutes.
Missing check = $412.20 - $331.60 = $80.6
Hope it helps!