Q=5w/4xz^2
Let's first see how each action affects Q individually and then we'll combine them.
Quadrupling means w is replaced by 4w. Replacing w with 4w in the above equation gives:
Q=5(4w)/4xz^2
=4*5w/4xz^2
=4Q
So quadrupling w quadruples Q.
Doubling x means x is replaced by 2x:
Q=5w/4(2x)z^2
=(1/2)(5w/4xz^2)
=(1/2)Q
So doubling x halves Q.
Tripling z means z is replaced by 3z:
Q=5w/4x(3z)^2
=5w/4x*9z^2
=(1/9)(5w/4xz^2)
=(1/9)Q
So tripling Z multiplies Q by 1/9
Taking all of these things together:
Q is multiplied by 4*(1/2)*(1/9)=2/9
Your other option is to just make up simple numbers for w,x, and z, plug them in, see what Q is. Then do the quadrupling, doubling and tripling, plug them in again and see what the new result is, and compare.
