Amount of salt in 15% solution + amount of salt in 20% solution=amount of salt in 16% solution.
0.15x=amount of salt in 15% solution
0.20*2 or 0.4=amount of salt in 2 liter solution
0.16*(x + 2)=amount of salt in 16% solution. x+2 represents the combined volume of the mixture of the 15% and 20% solutions poured together.
0.15x + 0.4=0.16(x + 2)
Let the individual amounts equal the combined amount and then solve for x.
0.15x + 0.4=0.16x + 0.32
Subtract 0.15x from both sides
0.4=0.01x + 0.32
Subtract 0.32 from both sides
Divide both sides by 0.01
Mix 8L of 15%solution with 2L of 20% solution.