Rs. 30
Given- Rs. 200
Exchange- 0.5x+2y+10z<200
Ratio- x/y/z=18/13/9
Cost of 2x chocolates=?
With minimum coefficient of 1, the amount will make 18*0.5+13*2+9*10=125 Rs., if doubled it will be greater than Rs. 200 so the exchange was Rs. 125.
5x chocolates cost Rs. 200- Rs. 125= Rs. 75, so 2x chocolates cost Rs. 2*75/5= Rs. 30