Question

In a figure If AB and CD are parallel, find the value of $x$

Answer 1

The adjacent angle of ${75}^o$ is $={180}^o-{75}^o={105}^o$

and we can see that ${105}^o$ and $(x+4x=5x)$ are alternate exterior angles

Mathematically, ${105}^o=5x\Rightarrow x={21}^o$