Supplementary angles are two angles whose measures add up to 180 degrees.
Given that \( m∠j = 34° \), we can set up the equation:
\[ m∠j + m∠k = 180° \]
Substituting the value of \( m∠j \):
\[ 34° + m∠k = 180° \]
To find \( m∠k \), we subtract \( 34° \) from \( 180° \):
\[ m∠k = 180° - 34° = 146° \]
Thus, \( m∠k = 146° \).