Answer: 3
Step-by-step explanation:
Perimeter is the value around the rectangular object. Since we already know that one side is 5 cm, the opposite side would be 5 also. That adds up so far as 10. The remaining 6 could be found by figuring out what two numbers add up to 6. Since 3 + 3 = 6 This concludes the missing side length as 3.