15.2 In the figure, $x=a^{\circ}, y=44^{\circ}, z=52^{\circ}$ and $w=b^{\circ}$. Find $b$.
$\begin{array}{l}x+w+y+z=180(\angle \mathrm{s} \text { in the same segment, } \angle \mathrm{s} \text { sum of } \Delta) \\ 36+b+44+52=180 \\ b=48\end{array}$