To find angle \( b \) using the properties of exterior angles of triangles, we can use the fact that the measure of an exterior angle is equal to the sum of the measures of the two non-adjacent interior angles.
Given:
- \( a = 142^\circ \)
- \( b \) is the exterior angle.
Since \( b \) is an exterior angle, it can be expressed as: \[ b = 180^\circ - a \]
Substituting the value of \( a \): \[ b = 180^\circ - 142^\circ \] \[ b = 38^\circ \]
Therefore, angle \( b \) is \( 38^\circ \).
The correct response is: 38°