If 3 = [tex]m^x[/tex], then we know 9 = [tex](m^x)^2[/tex] because 9 is 3 squared.
[tex](m^x)^2[/tex] can be simplified to [tex]m^{2x}[/tex]
So now we know [tex]9m^2[/tex] = [tex]m^{2x}[/tex]·[tex]m^2[/tex]
Since [tex]m^{2x}[/tex] and [tex]m^2[/tex] have the same base, we can express it as a single term by adding the exponents together.
So the answer is C) [tex]m^{2x+2}[/tex]