Answer:
First of all, we can see that this shape have 4 90° angles. 
 
Secondly, since x = 5 we have: 
 
 3 × 5 -2 = 15 - 2 = 13 (cm) 
 
And: 5 + 8 = 13 (cm) 
 
=> The two adjacent sides that make up the angle is equal to each other 
 
So this shape is a quare. 
 
=> This shape is a square.
Explanation: