Hey there! :D
These are vertical angles. They have the same measure, so they are equal to each other.
[tex]6x+25= 2x+105[/tex]
Subtract 25 on both sides.
[tex]6x=2x+80[/tex]
Subtract 2x on both sides.
[tex]4x=80[/tex]
Divide both sides by 4.
[tex]x=20[/tex]
I hope this helps, and have a nice day!
~kaikers