Question

~please only answer if you know for sure~ -Thank you-

Answer 1

ZW and DA are similar sides
WX and AB are similar sides.

Make a proprtion of the sides.

$\sf{ \frac{WX}{AB} = \frac{ZW}{DA} }$

Plug in the numbers

$\sf{ \frac{6}{24} = \frac{ZW}{18} }$

Cross multiply

$\sf{ 6\times 18=ZW \times 24$

And then solve for ZW

$\sf{ZW = 4.5}$

So our final answer is 

$\boxed{\bf{4.5~centimeters}}$

Hope that helps :P