Step-by-step explanation: you divide 9.45 by 5 and you get the unit rate of 1.89 and then you divide 13.68 by 8 and you get the unit rate of 1.71 which means the 8 pound bag is cheaper.
Since we want to know how far she goes every hour to multiply that by 4 to get how far she goes in 4 hours, we do 17/3.5 to get per hour miles = around 4.86. Multiply that by 4 to get around 19.43 miles