Perimeter is the length of all the sides added up.
Since each page is a rectangle, the side directly across from it is the same length as it. Here's a picture:

1.5 + 1.5 + 1.2 + 1.2 =
3 + 2.4 =
5.4
The perimeter is 5.4 meters!
If it helps you, draw it out! I'm personally more of a visual learner myself. :)