Question 212256
For your example, it's adding up all the numbers you've shown.  Since there are 3 you are finding the perimeter of a triangle.


Answer is 12 cm.


For a rectangle you would add up four sides where Perimeter P= 2(w+l) where w is the width and l is the length.  


Hope that was helpful?


For Step-By-Step free videos in Introduction to Algebra, please visit http://www.FreedomUniversity.TV/courses/IntroAlgebra and for Trigonometry visit http://www.FreedomUniversity.TV/courses/Trigonometry.


Good luck in your studies!


Respectfully,
Dr J