We want to isolate s, in order to do this we must first distribute the 4 inside of the parentheses, giving us the equation
8s-4=7s+12
It's always easier to not work with negatives, so instead of subtracting 12 from each side, we'll add 4 to each side
Leaving us with the equation 8s=7s+16
After that we'll subtract 7 from each side (we only want s on one side) this leaves us with the equation. 1s=16
So the value of s in this equation is 16