Question 135635
F varies jointly as x and y means {{{F=kxy}}} where k is the constant of variation.


For your problem:

{{{m=kn^2sqrt(q)}}}


You are given that {{{m = 24}}} when {{{n = red(2)}}} and {{{q = green(4)}}}, so:


{{{24=k(red(2))^2sqrt(green(4))}}} => {{{24=k(8)}}}, therefore {{{k=green(3)}}}


Now you can write:  {{{m=green(3)n^2sqrt(q)}}}


Finding m for n = 5 and q = 9 is a simple matter of substitution and arithmetic.