Michael J. answered 01/10/17
Tutor
5
(5)
Effective High School STEM Tutor & CUNY Math Peer Leader
Use this equation.
AB + BC = AC
AB + 2x + 3 = 4x - 12
Solving for x,
2x - 4x = -12 - 3 - AB
-2x = -15 - AB
x = (-15 - AB) / -2
Plug in this value of x into the line segments to find BC and AC.
BC = 2[(-15 - AB) / -2] + 3
BC = -(-15 - AB) + 3
BC = AB + 18
AC = 4[(-15 - AB) / -2)] - 12
AC = -2(-15 - AB) - 12
AC = 30 + 2AB - 12
AC = 2AB + 18
Makes sense to you? You did not specify an expression for AB, but this is how you would solve it in general. I guess you will fill in that gap yourself.