What is the axis of symmetry of h (x) = - 2x2 + 12x - 3?

The axis of symmetry is the x value of the vertex

we have a handy-dandy way of finding that from standard form, ax^2+bx+c=y

for

ax^2+bx+c=y

the x value of the vertex is - b/2a

y=-2x^2+12x-3

-b/2a=-12 / (2*-2) = - 12/-4=3

x=3 is the axis of symmetry