Answer:
x = 2
AB = 14
DC = 14
Step-by-step explanation:
If opposite sides are congruent, then:
AB = DC
AB = 3x + 8
DC = x + 12
Thus:
3x + 8 = x + 12
Collect like terms
3x - x = -8 + 12
2x = 4
Divide both sides by 2
x = 2
AB = 3x + 8
Plug in the value of x
AB = 3(2) + 8 = 14
DC = x + 12
Plug in the value of x
DC = 2 + 12 = 14
