Rectangle abcd is similar to rectangle efgh what is the length of fg

The smaller rectangle is 2/3 of the size so divide 12 by 3 then times (4) times 4 by 2 and u get 8 FG = 8 Youre correct

For this problem, we can set up a porportion to solve.

So, lets find two sides we already know the length of.
This would be EF, which is corresponding to AB.

We would write this as 12
                                     
                                       18.
We are trying to find the length of FG. Lets find the side in the bigger square that is corresponding to FG. This would be BC, which is 12.

So, lets add that to our porportion. Since we started with the smaller square, the 2nd porportion must also begin with the smaller square's side length on top, so it is equal. Since we do not know that length and that is what we are trying to find, we will just put an X in its place. Our final equation would look like this:

12        x
=
18       12

To find X, all we need to do is cross multiply. 12 times 12 is 144, divided by 18 is 8.

So, side FG is 8 yards.
We know this is correct, because if we divide 12 by 18 we get 0.6 repeating, same if we divided 8 by 12. This proves that they are similar, because they are equally porportional. 

Hope I could help!