Aline parallel to a triangle's side splits ab into lengths of x − 6 and x + 1. the other side, ac, is split into lengths of x and x + 21. what is the length of ac?
a)27
b)33
c)39
d)45
explain how you solved. do not comment unless you are sure you know the answer. i will give you brainliest for right answer.

AC = 39

Side Am/mB (x + 1)/(2x - 5)
Side Am/mC (x + 21)/(2x + 21)
m is the point where the parallel line is.
AB = AC
(x+1)/(2x -5) =(x +21)/(2x+21)
Cross multiply.
(x+1)(2x+21)=(2x-5)(x+21)
2x^2+23x+21=2x^2+37x-105
Subtract 2x^2 from both sides.
23x+21=37x-105
Subtract 23x from both sides.
21= 14x -105
Add 105 to both sides
126 = 14x
Divide both sides by 14
x = 9
Plug 9 back in for x in
2x + 21
2(9) + 21 = 39