What is the mole fraction, x, of solute and the molality, m (or b), for an aqueous solution that is 19.0% naoh by mass?

We will assume that the solvent is water. So, if we have 100 grams of the solution, 19 grams will be sodium hydroxide, while the remaining 81 grams will be water.

The molar weight of sodium hydroxide, NaOH, is 40. The molar weight of water is 18. Finding the moles of each:

NaOH:
19 / 40 = 0.475

Water:
81 / 18 = 4.5

Total moles present:
4.5 + 0.475 = 4.975 moles

The mole fraction of NaOH is:
0.475 / 4.975 = 0.0955

The mole fraction of NaOH is 0.0955

1.75 is the weight of one medium egg