Given:
Rate of reduction : 85%
Remaining volume: 120 ml.
This means that 120 ml is equivalent to 15% of the original volume.
100% - 85% = 15%
120 ml ÷ 15% = 800 ml.
There was 800 ml of water before it was reduced.
800 ml * 85% = 680 ml ⇒ volume reduced
800 ml - 680 ml = 120 ml ⇒ volume left after reduction.
