The first thing you should do is distribute 1/4 into (20x+8). You should do this first because of the order of operations:

Parenthesis
Exponent
Multiplication
Division
Addition
Subtraction

5x+2+3=0

Add 2 and 3 together

5x+5=0

Subtract 5 from each side.

5x=-5

Finally, divide each side by 5

x=-1

To check our answer, substitute -1 in as x

1/4(20(-1)+8)+3=0
1/4(-20+8)+3=0
1/4(-12)+3=0
-3+3=0
0=0

x=-1

Hope this helped! Tell me if you have any other questions! 🙂