This is the concept of algebra. from the given equation;
y-9+9=-17+9
The original equation was y-9=-17
The subtraction was undone by applying inverse operation of adding 9 to get;
y-9+9=-17+9
y=-8
The aim of doing this was to obtain the value of the unknown which is y
Axis of symmetry of h(x) is x = 0
for f(x) its x = 2
and for g(x) its x = 3
so its
option 3
add 4 i guess. i dont really know