Move the negative sign to the left
-4 = s - (-6/4)
Simplify 6/4 to 3/2
-4 = s - (-3/2)
Simplify brackets
-4 = s + 3/2
Subtract 3/2 from both sides
-4 - 3/2 = s
Simplify -4 - 3/2 to -11/2
-11/2 = s
Switch sides
s = -11/2
