Given the function
[tex]g(x)=-3x+1[/tex]You have to calculate g(12), that is the value of g(x) for x=12.
To do so, replace the x term by 12 and solve the calculation:
[tex]\begin{gathered} g(12)=-3\cdot12+1 \\ g(12)=-36+1 \\ g(12)=-35 \end{gathered}[/tex]