"Diagram"
Determine the value of m∠DCB.
Here, in the diagram it is forming supplementary angle,
[The two angles that gives 180° when they add up are called]
So, we can conclude that,
[ Put the values and formed the suitable equation. ]
Value of x is 25°.
Now, put the value in the expression 3x + 3 (measurement of m∠DCB)




The value of m∠DCB is 78°.
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