The length of BC is equivalent to 12 units
If the midpoint if Ac is B, then the expressions below are true;
AB+BC = AC
AB = BC
Given the following parameters
AB = x + 6, and
AC = 5x - 6
BC = x + 6
Substitute
x+6+x+6 = 5x - 6
2x+12 = 5x - 6
2x-5x = -6-12
-3x = -18
x = 6
Determine the measure of BC
BC = x + 6
BC= 6 + 6
BC = 12units
Hence the length of BC is equivalent to 12 units
Learn more on midpoint here: https://brainly.com/question/5566419
#SPJ1