Question

look at this diagram:
if $overleftrightarrow{df}$ and $overleftrightarrow{gi}$ are parallel lines and $m\angle fec = 48^\circ$, what is $m\angle dec$?

Explanation:

Step1: Identify supplementary angles

$\angle FEC$ and $\angle DEC$ form a linear pair, so they are supplementary (sum to $180^\circ$).

Step2: Calculate $\angle DEC$

Subtract $m\angle FEC$ from $180^\circ$.
$m\angle DEC = 180^\circ - 48^\circ$

Answer:

$132^\circ$