If $A (5, 3)$ and $B (3, 3)$,then the midpoint of $\overline{AB}$ is $\ldots \ldots \ldots .$

$\overline{AB}$ is given. If $P$ is a point on $\overline{AB}$ such that $P \neq A$ and $P \neq B$,then $P$ divides $\overline{AB}$ from $A$ in the division ratio $\ldots \ldots \ldots \ldots$

If $A(-2, 1)$,$B(1, 0)$,$C(x, 3)$,and $D(1, y)$ are the vertices of a parallelogram $ABCD$,then find the values of $x$ and $y$.

Which of the following groups is true for $\square ABCD?$

$1$. $\square ABCD$ is a rhombus.	$a$. $\overline{AC}$ and $\overline{BD}$ bisect each other.
$2$. $\square ABCD$ is a parallelogram.	$b$. $\overline{AC}$ and $\overline{BD}$ bisect each other at right angles.
$3$. $\square ABCD$ is a rectangle.	$c$. $\overline{AC}$ and $\overline{BD}$ are congruent and bisect each other at right angles.
$4$. $\square ABCD$ is a square.	$d$. $\overline{AC}$ and $\overline{BD}$ are congruent and bisect each other.

The line segment joining $(0,0)$ and $(6,6)$ is divided into four congruent parts. Which of the following is one of the dividing points?

If the midpoint of a line segment joining $(3, 4)$ and $(a, 8)$ is $(4, 6)$,then $a = \ldots$