m% salty

Question A Chemist has m gm of salt water that is m% salty.How many grams of salt must be add to make a solution that is 2m % salty? Answer At m% salty m gm of salt water has m2 /100 gm salt At 2m% salty water  the amount of  salt to be added is derived from the equation as bellow   2m/100=m2+x/x+m   Solve and get x=m2/100-2m