Answer:
120
Step-by-step explanation:
ABC is a straight line so it is equal to 180
ABC = ABD + DBC
180 = 2x + x+90
Combine like terms
180 = 3x+90
Subtract 90 from each side
180-90 = 3x+90-90
90 = 3x
Divide each side by 3
90/3 = 3x/3
30 =x
We want to find DBC
DBC = x+90
= 30+90
= 120
