We start by drawing the segments:
We can write that AB+BC=AC:
[tex]\begin{gathered} AB+BC=AC \\ 3+(4x+1)=16 \\ 4x+1=16-3 \\ 4x+1=13 \\ 4x=13-1 \\ 4x=12 \\ x=\frac{12}{4} \\ x=3 \end{gathered}[/tex]Then, with thevalue of x, we can calculate BC. But, a simpler way is to use AB+BC=AC:
[tex]\begin{gathered} AB+BC=AC \\ BC=AC-AB=16-3=13 \end{gathered}[/tex]The answers are x=3 and BC=13.