Hi!
So, first, let's just form the equation:
We know that all the side lengths equal 12 cm.
So the equation will be:
5 + 3 + x = 12
The answer you put in the box is:
5 + 3 + x
To find the value of x, we just solve this equation:
5 + 3 + x = 12
Combine like terms:
8 + x = 12
Same to both sides:
x = 12 - 8
x = 4
I hope this helped, let me know if you have any questions.
