Final answer:
To find the length of segment BC on a line, you need to know the value of x and substitute it into the expression 8x.
Step-by-step explanation:
To find the length of segment BC, you need to know the value of x. Once you know the value of x, you can substitute it into the expression 8x to find the length of segment BC.
For example, if x = 2, then the length of segment BC would be 8 * 2 = 16 units.