Let Mohan earns x amount, then the amount earned by Kumar is 1.25x and by Raman is 1.75x.
Given Ramans Monthly income is 1750, that is 1.75x=1750. Therefore x= 1750/1.75=1000.
The income of Kumar is 1.25 x 1000=1250
The combined income of all the three= 1000+1250+1750=4000
Mohan's salary as a percentage of the combined salary of the three colleagues= (1000/4000) x 100 = 25%