This problem is about middle points. Remember that a middle point divides equally the intersected segment, that means segments DC and CE are equal, so we can solve as follows
[tex]DC=CE[/tex][tex]6+x=2x+1[/tex]Now, we have a linear equation. First, we need to put all terms with variables on the left side, and terms without variables on the right side-
[tex]x-2x=1-6[/tex]Now, we solve each difference
[tex]-x=-5[/tex]We need to multiply by -1 to have the variable positive
[tex]x=5[/tex]