Question

Find mDEC
A) 90
B) 95
C) 100
D) 120​

Answer 1

C) 100

Explanation:

line AC intersects line DB,

hence ∠AEB and ∠DEC are opposite angles and thus

∠AEB = ∠DEC

5x-10 = 4x+12 (subtract 4x from both sides)

5x - 4x - 10 = 12

x - 10 = 12 (add 10 to both sides)

x = 12 + 10 = 22 degrees

∠DEC = 4x+12

= 4(22) + 12

= 88 + 12

= 100 degrees