Answer:
90 g/100 g water
Explanation:
I’m guessing that “they” are asking you to interpret a solubility curve something like the one below.
Find the point at 50 °C on the horizontal axis.
From there, draw a vertical line until it meets the solubility curve of KNO₃.
Then, draw a horizontal line to the solubility axis.
It appears to hit the axis at about 90 g/100 g water.
Thus, the solubility of KNO₃ at 50 °C is 90 g/100 g water.