Question

Assume that ABD has a measure of 105.

Assign a variable and write an equation that will help you determine the measure of DBC.

Answer 1

75

Explanation:

So it is asking for the missing angle. Simply make an equation to find it.

X+105=180

X=180-105

X=75

Therefore 75 degrees is your answer.

Answer 2

We'll use the variable x.

105+x=180 <-- equation

105-105+x=180-105

x=75 <-- missing angle