Let the cost price of the cycle be x

Please note here that if my profit on x is p%, then the total amount can be written as : px/100 + x= x(p+100)/100, this is what we will use ahead

then A sold it to be for : x+ (12.5/100)x = (112.5/100)x

and B sold it to C for : (115/100)*(112.5/100)x and this is given to be 20

So equating, we get:

x= (20*100*100)/(115*112.5) = Rs. 15