Answer: x=4 
Explanation:
We know that line segment AC= AB + BC 
we also know that AB= 3x+8 and BC= 2x-5
by substituting these, we get AC= (3x+8)+(2x-5)
AC is given as being 23, so we know that 
23= (3x+8)+(2x-5)
by combining like terms, we get that 
5x+3=23
simplify this to get that x=4