The numbers -9 and -4
Hope this helped :)
39/1.5 = 26 km per hour
51/3 = 17 km per hour
Then you need the mean. 26+17/2 = 21.5 km per hour
The weight is proportional to the price. So if 10lb cost $18.24, quarter as much (2.5lb) would cost four times less($18.24÷4=$4.56).