Start by figuring out the smallest square. That is one unit. There are two of the smallest squares that have the same length as the next size of the square, which has 2 unit squares.

This makes square X a total of 3 of the unit square lengths (length of X is 3 times length of the smallest square). Since X has a length of 6, the smallest square has a length of 2cm.

Now that you have the length of the smallest square, you can figure out how many of the smallest squares make up Y. From there you can get the length of Y, and hence its perimeter (ans: 104cm).