It might be x=8, bear with me because it’s been awhile, but I believe that bisect means cut into 2 equal pieces so angle ABD is 4x+8 so DBC also has to equal 4x+8. And the whole angle together is 80 degrees. So you would add 4x+8 and 4x+8 equal to 80. You would get 8x+16=80. So then you would subtract 16 on both sides and get 8x=64. Then divide by 8 to get x by itself to get the answer which is 8. If that isn’t it then I am terribly sorry. But that’s my best answer I honestly got for ya man.