Remember: Always deal with brackets first.
When there is a negative just outside the brackets, it is the same as it being negative 1. So:
8x -1(3x+10) = 34
To get rid of the brackets, multiply -1 x 3 and -1 by 10. That gives:
8x - 3x - 10 = 34
Get the x's on one side and the numbers on the other. The x's are already conveniently on the same side. However, you need to move the 10 to the right side, so change the sign from negative to positive:
8x - 3x = 34 + 10
Subtract on left and add on right:
5x = 44
You want x alone, without the 5. 5x just means 5 times x. To get rid of multiplication, you need to divide. Divide both sides by 5.
5x ÷ 5 = 44 ÷ 5
That will erase the 5 from the left side. On the right side, another way to write 44 ÷ 5 is as the fraction 44 over 5. They mean the same thing. So:
x = 44/5
That is the fraction 44 over 5. Can we simplify it? Not really, since you can't divide an even number like 44 by 5. So, the answer you have is complete.
P.S. You only need to write it as a decimal if the question asks you to (for example, to give your answer to 1 decimal point).