Question 1089942

2.

If {{{AB = 5x}}}, {{{BC = 2x –4}}}, and {{{AC = 52}}}, then {{{x = 8}}}

from your image I see that 

{{{AC =AB+BC }}}...substitute given values
{{{52 =5x+2x-4}}}
{{{52+4 =7x}}}
{{{7x=56}}}
{{{x=56/7}}}
{{{x=8}}}


3.
 Write a two-column proof.

Prove: If {{{AB = CD}}}, then {{{AC = BD}}}

statement............................reason
1.{{{AB = CD}}}.............................given
2.{{{AB+BC=AC}}}............................segment addition postulate
3.{{{BC+CD=BD}}}............................segment addition postulate
4.{{{AB+BC=BC+CD}}}.........................substitution
5.{{{AC = BD}}}.............................subst. prop. of =