What mass of 5.0% by weight NaCl solution is necessary to yield 3.2g NaCl?

Question

please help me with this problem

Answer 1

3.2 g / 0.05 = 64 g

5% = 0.05 in decimal form

64 g x 0.05 = 3.2 g

64 g = 3.2 g / 0.05

Answer 2

Not so super-duper tough.  Just divide the grams of NaCl by the weight fraction of NaCl in solution.   You get this by mass balance.  If X is the weight of solution, 0.05X= 3.2 grams.