The directions for mixing an insect spray say to use 1 3/4 ounces of chemical in each gallon of water. how many ounces of chemical should be mixed with 4 1/5 gallons of water?

Since 1 3/4 oz. chemical / 1 gallon water, convert that to an improper fraction--> 7/3oz./gallon water.
Now convert the new water gallons to an improper fraction: 4 1/5 gallons
--> 21/5 gallons
Now 21/5 gallons water × 7/3oz./gallon water = 21×7/5×3 = 7×7/5 = 49/5oz.--> convert to mixed number: 9 4/5oz. chemical in order to make 4 1/5 gallons of mixture.