Answer:
The value of k = 16 and the measure of unknown angle is 48°
Explanation:
=> 84°+48°+3k° = 180° { The sum of angles of a triangle is 180° } 
=>  132°+3k° = 180° 
=> 3k° = 180°-132° 
=> 3k° = 48°
=> k = 48/3 
=> k = 16 
The measure of unknown angle is 3×k = 3×16 = 48°