First, use distributive property to remove the parentheses. You do this by multiplying-8 by 2 and -3x.
-8(2-3x)=104
24x-16=104
16 is a constant, which should be moved away from the variable by adding 16 to both sides. That removes the 16.
24x -16 +16 = 104 + 16
24x = 120
Now divide by 24 on both sides to remove the coefficient
24x/24 = 120/24
That should leave you with 5.
x= 5