$A$ part [or portion] of a line with two end points is called a $\ldots \ldots \ldots$

$A$ part of a line with one end point is called a $\ldots \ldots \ldots .$

If one of the two angles of a linear pair has measure $x^{\circ},$ then the other angle has measure of $\ldots \ldots . .$

In the figure,$OD$ is the bisector of $\angle AOC$,$OE$ is the bisector of $\angle BOC$,and $OD \perp OE$. Show that the points $A, O$,and $B$ are collinear.

In the given figure,if $PQ \parallel RS$ and $RS \parallel TU$,and $y: z = 7: 8$,find $x$.

$\angle P$ and $\angle Q$ are complementary angles. If $\angle P = 3x + 15^{\circ}$ and $\angle Q = x + 7^{\circ}$,then find $\angle P$ and $\angle Q$.