Respuesta :

Answer:

8

Step-by-step explanation:

Perimeter = Sum of all side lengths

If perimeter = 20, then 5 + 3 + 4 + x = 20

( where x = missing side length )

5 + 3 + 4  = 12

12 + x = 20

20 - 12 = 8

Hence, x = 8

The answer would be 8
Step by step
5+3= 8
8+4=12
20-12=8