Answer: [tex]\overline{BC}=36\text{ units}[/tex]
Step-by-step explanation:
Given : [tex]\overline{BC}[/tex] with point D between points B and C.
Also, [tex]\overline{BD}\cong\overline{DC}[/tex]
We know that the measurement of congruent line segments are equal.
Therefore,
[tex]\text{Length of }\overline{DC}=\text{Length of }\overline{BD}=18\text{ units}[/tex]
Now, [tex]\overline{BC}=\overline{BD}+\overline{DC}[/tex]
[tex]\Rightarrow\overline{BC}=18+18=36\text{ units}[/tex]
Hence, [tex]\overline{BC}=36\text{ units}[/tex]