Awater tank hols 540 galloms but is leaking at a rate of 4 gallons per week a second water tank holds 720 gallons but is leaking at a rate of 7 gallon per week after how many weeks will the amount of water in the two tanks be the same

Let after n week both tanks have same quantity of water .

for first tank

tank hold 540 gallon of water ,
leaking of water 4 gallon /week
so, in n week water leak from the tank =4× n = 4n

now, after n week quantity of water in the tank = 540 -4n

for second tank

quantity of water in the tank =720 gallon
leaking of water at the rate = 7gallon/week
so, after n week water leak from the tank = 7× n =7n

after n week quantity of water rest in the tank = 720 -7n

now ,
according to question ,

water in first tank = water in second tank
540 -4n = 720 -7n

7n -4n = 720 -540

3n = 180

n = 60

hence , after 60 week both tank have same quantity of water.