Solubility is a function of temperature. But for this case solubility is not given at that certain temperature and it is somewhat difficult to find for certain datas. I would be using the solubility at 20 degrees celsius which is 1.85g/100g Water
.0185 g / g water = g barium hydroxide / 100 g
1.85 g of barium hydroxide can be dissolved in 100 g of water.
Hope this could help. Have a nice day.