I keep getting answer wrong. I don't know what I did wrong. I really need help please. I need help with 1 question. Can you help with this please if you don't mind?

Question

1) Suppose you are given that z = c y^3/x^2 where c is some number. For a particular value of c, x and y, z is equal to 136. Suppose x is decreased by a factor of 2 and y is decreased by a factor 6.5. What is the new value of z?

Answer 1

a prime (')
denotes the newer number.

z'/z = z'/136 = (y'/y)^3*(x/x')^2
= (1/6.5)^3*2^2 = 0.014565
z' = 1.981