pharmacist has an 18% alcohol solution and a 40% alcohol solution. How much of each should he mix together to make 10 liters of a 20% alcoho

sum of ingredients = sum of the products

 

.18 x           +     .4 (10 - x)         =   .20 (10)        solve for 'x' the liters of 18%      then   40 % will be 10 -x   liters