How many grams of a 20% sodium chloride solution can be obtained by adding salt to 200 g of a 10% solution?

Given:
ω3 (NaCl) = 20%
m1 solution (NaCl) = 200 g
ω1 (NaCl) = 10%

To find:
m3 solution (NaCl) -?

Solution:
1) m1 (NaCl) = ω1 (NaCl) * m1 solution (NaCl) / 100% = 10% * 200/100% = 20 g;
2) Let m2 (NaCl) = (x) r;
3) m3 (NaCl) = m1 (NaCl) + m2 (NaCl) = (20 + x) g;
4) m3 solution (NaCl) = m1 solution (NaCl) + m2 (NaCl) = (200 + x) g;
5) ω3 (NaCl) = m3 (NaCl) * 100% / m3 solution (NaCl);
20% = (20 + x) * 100% / (200 + x);
x = 25;
6) m3 solution (NaCl) = 200 + x = 200 + 25 = 225 g.

Answer: The mass of the NaCl solution is 225 g.