how do you do solution problems in algebra?

Question

karls science experiment require 24% NaCl solution. he has 50mL of 40% NaCl solution and a large quantity of 20% NaCl solution. How much 20% solution should karl add to the 50mL of 40% solution in order to produce 24% solution?

Answer 1

hav 50cc av 40%

add x cc av 20%

want 24%

50*0.4 +0.2*x=0.24*(50+x)

20 +0.2x=12 +0.24x

0.24x -0.2x=20 -12

0.04x=8

x=8/0.04

x=200