Final answer:
To find the length of line AB, we use the fact that line DB is a median of the triangle ABC. Line DC is also x, since line DB is a median, and given that BC = 20, we can solve for x to find that AB = 10 units.
Step-by-step explanation:
To find the length of line AB, we need to use the fact that line DB is a median of the triangle ABC. In a triangle, a median is a line segment that connects a vertex to the midpoint of the opposite side. Since line DB is a median, it divides side AC into two equal halves.
Let's assume that the length of line AB is x. Since line DB is a median, line DC is also x. Therefore, we have AC = x + x = 2x.
Given that BC = 20, we can use the fact that the medians of a triangle divide the opposite side into segments of equal length. This means that DC is also equal to 20. Therefore, we have 2x = 20, and solving for x gives x = 10.
So, the length of line AB is 10 units.