Given the information, we can model the capacity of Tank A with the following relation function:

where 'y' are the liters inside the tank and x is the minutes that pass.
To find out how many liters of water are n Tank A after 80 seconds, first we must covert 80 seconds to minutes:

then, doing x=4/3, we get:

therefore, after 80 seconds, there are 136 liters in Tank A.
The expression fo know how many liter