Answer:
1) congruent
2) corresponding angles
3) 3x+21 = 6x-60
4) x =9
Step-by-step explanation:
1) congruent becuase supplementary means that these 2 angles add up to make 180 degrees.
2) the file below
3) we know they are equal because the congruent correspoding angles.
4) 3x+21 = 6x-60
=> 21 = 9x-60
=> 81 = 9x
=> 9 = x
