Answer:
Answer is D.
Step-by-step explanation:
[tex]v^{2} =\frac{3P}{mn}\\[/tex]
Multiply both sides by m.
[tex]mv^{2} =\frac{3P}{n}\\[/tex]
Divide both sides by [tex]v^{2}[/tex].
[tex]m =\frac{3P}{nv^{2}}\\[/tex]