3x-4=13
First you want all your x's on one side, and all your ordinary numbers on the other.
Add four to both sides to get rid of the "-4" part on the left.
Your new equation is 3x = 17
Divide each side by 3 to find X.
x= 17/3 or 5 2/3
Assuming CDB is a straight line then angle ADB = 180-82=98