Question 228620
Assuming that there are only three tanks, this means that the percentages must add to 100%. So let 'x' be the unknown percentage used by the center tank. Now add up the percentages and set them equal to 100 to get: {{{45+32.5+x=100}}}. 



Now solve for 'x' to get {{{77.5+x=100}}} ---> {{{x=22.5}}}


So the center tank used 22.5% of the fuel. Now just multiply the total amount of fuel (1680) by 0.225 (the decimal representation of 22.5%): 1680*0.225=378


So the center tank used 378 gallons of fuel.