Question 920689
{{{x}}}= the length of AB
Since B is the midpoint of AC {{{x}}}= the length of BC too,
and the length of AC is the sum of the lengths of AB and BC.
so {{{x+x=23.8}}}--->{{{2x=23.8}}}--->{{{x=23.8/2}}}--->{{{highlight(x=11.9)}}}