Which two of the following line segments are midsegments of $\triangle ABC$△ABC?
$\overline{AB}$AB
$\overline{DF}$DF
$\overline{BC}$BC
$\overline{BF}$BF
$\overline{DE}$DE
$\overline{AC}$AC
Consider the following figure:
Determine the value of $a$a in the following triangle:
Consider the following figure: