Step-by-step explanation:
slope=4-6/8-3=-2/5
chosing another point (x,y) we have
y-4/x-8= -2/5
y-4=-2/5(x-8)
y= -2/5x+16/5+4
Let the equal sides of the isosceles Δ ABC be x.
Given that the perimeter of Δ ABC = 50m.
Therefore, 2x + AC = 50 --- (1)
It is also given that the perimeter of Δ ABD = 40m.
Therefore, x + BD + AD = 40
BD is the median of the Δ ABC. Therefore, D is the midpoint of AC.
So AD = CD.
Or, AD =
AC
Therefore, 
Multiply both sides by 2.
2x + 2BD + AC = 80
From (1), 2x + AC = 50.
Therefore, 2BD + 50 = 80
2BD = 80 - 50
2BD = 30
BD = 15m.
The correct answer here would be the third choice or NK
hope this helps
Notice the 7) 1st sequence, and the 8) second one