Convert 15% to a decimal. When converting percents to decimals, move decimal 2 digits to the left: .15
Find 15% of 1000 gallons: .15 x 1000 gallons = 150 gallons
So the new machine uses 150 gallons less:
Old Machine gallons - 15% of Old Machine gallons = New machine gallons
1000 gallons -150 gallons = 850 gallons
