DB should equal CB plus DC.
First write an expression to represent DC.
(x+168)-(3x+134)
x+168-3x-134
-2x+34
Then write an equal for DC plus CB equals DB
-2x+34+71= 153+2x
-2x+105= 153+2x
-4x+105=153
-4x=48
x= -12
Now plug in the value of x to find DB
153+2(-12)
153-24
129
Final answer: 129
