Afunction is given by the equation h (x)=x 2 squared +6x-3. what is h (3)?

Your "h (x)=x 2 squared +6x-3" is ambiguous.  If you meant "x squared," then you need only write x^2  OR  "x squared," but NOT "x 2 squared."

I will assume that by  "h (x)=x 2 squared +6x-3" you actually meant:

h(x)=x^2 +6x-3.  To find h(3), subst. 3 for x:  h(3) = (3)^2 + 6(3) - 3, or

h(3) = 9 + 18 - 3, or h(3) = 24.