Answer:
m∠ACD = 76
Step-by-step explanation:
m∠A = (4x + 15)
m∠B = 21
m∠C = (180 -(7x + 6))
all triangle measures add up to 180
(4x + 15) + 21 + (180 -(7x + 6)) = 180
(4x + 15) + 21 + (180 -7x - 6) = 180
4x + 36 + 174 - 7x
210 - 3x = 180
-3x = -30
x = 10
7(10) + 6 = 76
Check:
180 - 76 = 104
4(10) + 15 = 55
21 + 55 + 104 = 180
