Evaluate the solution of the following problem

Problem- a tank initially contains 20 gallon of pure water. Brine containing 2 lbs. of salt per gallon enters the tank at a rate of 3 gal/min and the well-mixed solution exits at the same rate.

Part 1- Find the amount of salt in the tank after 5 minutes? Solve Using Differential Equations, show ro and any equations used please.

I want experts assist to determine the amount of salt in the tank.