You can use the cosine rule for this - you might have to change some of the letters around for it to make sense though. Hope this helps!
Answer:
1/2
Step-by-step explanation:
1/4 (4x - 8) + 3x =0
distribute the 1/4
x-2+3x=0
combine like terms
-2+4x=0
move -2 to the other side [by ADDing +2 to each side
4x=2
divide [by 4 on both sides]
x=1/2
This is what i got in the caculator 6400 if not im so so sory