Mock Set 1 Paper 01 Non Calculator

\begin{aligned} &\text{Given } x:y = 3:1,\; \text{let } x = 3k,\; y = k. \\ &\text{In } \triangle ABD,\; x + 2y = 180^\circ \\ &3k + 2k = 180^\circ \Rightarrow 5k = 180^\circ \Rightarrow k = 36^\circ. \\ &y = 36^\circ,\; x = 108^\circ. \\ &\text{Since } D, B, C \text{ are collinear, } w + y = 180^\circ, \\ &w = 180^\circ - 36^\circ = 144^\circ. \end{aligned}