Question 142905
I assume you meant Q(-3) not A(-3).

Given the expression {{{Q(x) = x^2 -3x +4}}}

You are then asked to find the value of Q at 3 different values of x.

In each case, you substitute the given value of x into the expression. 

So, for Q(2) (read that as "the value of the expression Q when x equals 2"), replace x everywhere with the number 2 as follows.
{{{Q(x) = x^2 -3x +4}}}
{{{Q(2) = 2^2 -3*2 +4}}}
{{{Q(2) = 4 -6 +4}}}
{{{Q(2) = 2 }}}

Next you are asked to find Q(-3). (read that as "the value of the expression Q when x equals -3"). Again, replace x everywhere with the number given for x; in this case -3 as follows.

{{{Q(x) = x^2 -3x +4}}}
{{{Q(-3) = (-3)^2 -3*(-3) +4}}}
{{{Q(-3) = 9 + 9 +4}}}
{{{Q(-3) = 22 }}}

You do Q(0). Let me know if you still don't understand.