Question

A biologist has three salt solutions: some 5% solution, some 15% solution, and some 25% solution. She needs to mix some of each to get 48 liters of 18.75% solution. She wants the number of liters of the 25% solution to be equal to one liter less than the sum of twice the number of liters of the 5% solution and the number of liters of the 15% solution. How many liters of each solution should she use?

I've been trying this for hours, I just don't know where to starts. :(

Answer 1

If the amounts are x,y,z then we have

x+y+z = 48
.05x+.15y+.25z = .1875*48
z = 2x+y-1

now just solve for x,y,z