Answer: In 20 minutes, tanks A and B will each have 120 gallons remaining in them.
Step-by-step explanation:
The equation, the amount at which they will be equal, represents the given starting amounts minus the gal/min times the unknown time in minutes, m.
220 - 5m = 180 - 3m Subtract 180 from both sides; add 5m to both sides.
220-180 -5m +5m = 180-180 +5m - 3m Combine like terms
40 = 2m Divide both sides by 2
20 = m
Check: Substitute 20 for m in the equation
220 - 5(20) = 180 - 3(20)
220 - 100 = 180 -60
120 = 120 True!
