15
The segment addition postulate states that if AC is a line with point B, then AB + CD must equal AC.
Setting Up the Equation
Using the postulate above we can set up an equation that is set equal to BD.
Now, rewrite this using the information we are given in the question.
Solving For BC
Now, we can solve this equation using the properties of equality.
To solve you need to isolate BC. Do this by subtracting 2 from both sides.
This gives us the answer, 15.
