The difference between the sums of two supplementary angles and two complementary angles is 

In the adjoining figure, $AB$ is perpendicular to both the lines $l \mathrm{and} m$. Now, we get 

In the adjoining figure, $l\parallel BC$ and $AB \mathrm{and} AC$ are the trasversals. If $\angle 2=\angle 3$ and $\angle 1=\frac{1}{4}\angle 2$, then the measure of $\angle B$ is