the answer is 20%. because :-
lets assume raman's income to be 100. then mohan's income is 125 (25% more than raman. so 100 + (25% of 100) f= 125)
in this scenario if we calculate raman's income basis mohan's then
mohan has 25 rupees more than raman.
hence, 25 / 125 *100 = 20%