Since angles ∠1 and ∠2 are supplementary, their measures add up to 180 degrees. Given that \( m∠1 = 77° \), we can express this relationship with the following equation:
\[ x° + 77° = 180° \]
Where \( m∠2 = x° \).
So the correct response is:
x° + 77° = 180° (x plus 77 degrees equals 180 degrees).