5+x/8=-3.
The goal in every equation is to get x by itself so when we're done it looks like x = __answer__.
Start by getting rid of the 5, which means we have to subtract it from the left side. Now, and this is important to remember, whatever we do to one side of the equation...

4(x-3) = 4.
Well, you know 4 x 1 =4, so in this case say x-3=1. You don't even have to expand it to know the answer is 4, and it's that easy!
You can distribute it to say 4x-12=4 and solve from there, but I like to take the easy route when I notice shortcuts. Why do more...

to put it simply, the answer is 9, as the others indicated. The great thing about math is you can always double check your answer by putting the number in the equation to see if it makes sense. 7-5=2, so just by logical reasoning you can see that 7-9=-2, and the answer makes sense!
Just...