9514 1404 393
Answer:
14 units
Explanation:
The angle bisector divides the sides proportionally.
BD/BA = CD/CA
(x+4)/8 = (2x+1)/12
3(x +4) = 2(2x +1) . . . . . multiply by 24 (the least common denominator)
3x +12 = 4x +2 . . . . . . . eliminate parentheses using the distributive property
12 = x +2 . . . . . . . subtract 3x
10 = x . . . . . . . . . subtract 2
Then the length of BD is ...
BD = x +4
BD = 10 +4 . . . . substitute the value of x
BD = 14