0.53 g of an organic compound $(\mathrm{x})$ when heated with excess of nitric acid (concentrated) and then with silver nitrate gave 0.75 g of silver bromide precipitate. 1.0 g of $(\mathrm{x})$ gave 1.32 g of $\mathrm{CO}_2$ gas on combustion. The percentage of hydrogen in the compound $(x)$ is $\_\_\_\_$ %. [Nearest Integer]

[Given: Molar mass in $\mathrm{g} \mathrm{mol}^{-1} \mathrm{H}: 1, \mathrm{C}: 12, \mathrm{Br}: 80, \mathrm{Ag}: 108, \mathrm{O}: 16$; Compound (x) : $\left.\mathrm{C}_{\mathrm{x}} \mathrm{H}_{\mathrm{y}} \mathrm{Br}_{\mathrm{z}}\right]$

The total number of structural isomers possible for the substituted benzene derivatives with the molecular formula $\mathrm{C}_9 \mathrm{H}_{12}$ is________.

The hydrocarbon $(\mathrm{X})$ with molar mass $80 \mathrm{~g} \mathrm{~mol}^{-1}$ and $90 \%$ carbon has _______ degree of unsaturation.

The possible number of stereoisomers for 5-phenylpent-4-en-2-ol is ________.