To solve for \( m\angle 7 \), we can use the property of angles formed by two intersecting lines.
Given that \( m\angle 6 = 140^\circ \), we need to find its adjacent angle \( m\angle 7 \). Since angles 6 and 7 are adjacent, we can use the fact that adjacent angles on a straight line sum up to \( 180^\circ \).
\[ m\angle 6 + m\angle 7 = 180^\circ \]
Substituting the value of \( m\angle 6 \):
\[ 140^\circ + m\angle 7 = 180^\circ \]
Now, we can solve for \( m\angle 7 \):
\[ m\angle 7 = 180^\circ - 140^\circ = 40^\circ \]
Thus, the answer is:
40°