Correct option is (c) 120 men
The work of 3 boys = the work of 2 men.
∴ the work of 75 boys = \(\frac 23\) × 75 men
= 50 men.
So, 50 men finish the work in 24 days.
∴ In 20 days the work is finished by 50 × \(\frac{24}{20}\) days = 60 men.
∴ Double the work will be finished by 60 × 2 men = 120 men.