0 = -x - 3
Add x to both sides of the equation.
x = -3
-3 is ≤ 1 so -3 is a solution to f(x) = 0
0 = x/2 + 1
Subtract 1 from both sides.
-1 = x/2
Multiply both sides by 2 .
-2 = x
-2 is not > 1 so -2 is not a solution to f(x) = 0
The only value of x that makes f(x) = 0 is -3
So the sum of all values of x such that f(x) = 0 is just -3 .