Answer: -2x - 2h + 6
Step-by-step explanation:
Anywhere you see an x, replace it with x+h like so
g(x) = 6 - 2x
g(x) = 6 - 2(x)
g(x+h) = 6 - 2(x + h)
g(x+h) = 6 - 2x - 2h
g(x+h) = -2x - 2h + 6
The order of the terms doesn't matter so you can arrange those 3 terms however you want.