Her speed is minutes per foot or feet per minutes, so we have 10 minutes/-200 feet=-1/20 feet. Since it doesn't matter that it's negative (we care about the speed, and you can't have negative speed), we get the absolute value (1/20). For the next 20 minutes, we have |20 minutes/-300 feet|=1 minute/15 feet. Since 1/20=0.05 and 1/15 is 0.0666667, 1/15 is clearly higher and the 20 minute portion was at a faster rate