You're asking for the percent by mass of a solution. Here's how to calculate it:

1. Convert grams to kilograms:

* 2.19 g NaCl = 0.00219 kg NaCl

2. Calculate the percentage:

* (Mass of solute / Mass of solution) x 100%

* (0.00219 kg NaCl / 0.075 kg solution) x 100% = 2.92%

Therefore, the solution contains 2.92% NaCl by mass.