f(x) = -x + 2
f(-1) This means that they want you to find the value of f(x) or y when x = -1.
f(x) = -x + 2 Substitute/plug in -1 into "x" since x = -1
f(-1) = -(-1) + 2 (two negative signs cancel each other out and become positive)
f(-1) = 1 + 2
f(-1) = 3
