Let the original price be x.
After a discount of 20%, was effected.
It means the value was reduced to: (100% - 20%) = 80% of the original value
80% of x = 100
(80/100)*x = 100
8x/10 = 100
8x = 10*100
x = (10*100)/8
x = 125
Original price = Rs.125
Option C.