Please provide steps
20% work in 3 days
So 100% work can be finished in 15 days.
80% of the work was completed by B in 20 days.
So he can do the 100% work in 25 days
A+B B 15d 25d
So the efficiency of A and B is 5
Efficiency of B alone is 3.
From that, efficiency of A is 2.
Now the total work ÷ A's efficiency = 75÷2=37.5