Acid-base indicator changes color based on pH.
drop some in a solution n watch the color changes. different indicators show different colors at different pH. they usually have standard colors for comparison.
You didn’t post the photo or full question
There are 2 sig figs in 0.092
The solubility rules usually go on to say that group IIA sulfides are soluble, but actually group IIA sulfides react with water to make H2S and the group IIA metal hydroxide.