Question

Tank A contains 35 gallons of water and is increasing at a rate of 5 gallons per minute. Tank B contains 100 gallons of water and is decreasing at a rate of 8 gallons per minute. In how many minutes will the tanks contain the same amount of water?

Answer 1

35+5t=amount in tank A after t minutes
100-8t=amount in tank B after t minutes

same amount

35+5t=100-8t
add 8t both sides
35+13t=100
minus 35 both sides
13t=65
divide by 13 both sides
t=5
5 minutes