Question

two parallel lines, e and f, are crossed by two transversals. what is the measure of $angle15$?$\bigcirc$ $mangle15 = 77^circLXB0\bigcirc$ $mangle15 = 93^circ$$\bigcirc$ $mangle15 = 97^circ$

Explanation:

Step1: Identify supplementary angle

$\angle 12$ and $97^\circ$ are supplementary, so:
$m\angle 12 = 180^\circ - 97^\circ = 83^\circ$

Step2: Relate to $\angle 15$

$\angle 12$ and $\angle 15$ are alternate interior angles (parallel lines $e,f$ cut by transversal $d$), so they are congruent:
$m\angle 15 = m\angle 12$

Answer:

B. $m\angle 15 = 83^\circ$