Step 1. The expression that we have is:
[tex]x-y^2[/tex]And we are given the following values for x and y:
[tex]\begin{gathered} x=12 \\ y=3 \end{gathered}[/tex]Step 2. To find the value of the expression, we need to substitute the values of x and y:
[tex]x-y^2=12-3^2[/tex]Step 3. Before making the subtraction we solve the exponent. 3^2 is equal to 9:
[tex]12-9[/tex]Finally, the result of the subtraction is:
[tex]12-9=\boxed{3}[/tex]Answer:
3