The length of line BE on the given line segment is 3.5 m.
The given parameters:
The sketch of the given line segments is presented in the diagram uploaded.
The length of BE is determined by applying similar triangle theorem as follows;
[tex]\frac{CB}{AB} = \frac{BD}{EB} \\\\\frac{15 + 3}{21} = \frac{3}{EB} \\\\18EB = 63 \\\\EB = \frac{63}{18} \\\\EB = 3.5 \ m[/tex]
Thus, the length of line BE on the given line segment is 3.5 m.
Learn more about similar triangle here: https://brainly.com/question/11899908