Explanation:
what is the problem ?
as indicated you only need to use the corresponding value as "x" in the formula and then just calculate the result.
g(-1) = 3 - 1/3 × -1 = 3 + 1/3 = 3 1/3 or 10/3 or 3.333...
g(0) = 3 - 1/3 × 0 = 3
g(4) = 3 - 1/3 × 4 = 3 - 4/3 = 9/3 - 4/3 = 5/3 or 1 2/3 or 1.66666...