find the missing side length in the image below

Answer:
The missing side length is of 5.
Step-by-step explanation:
The sides are proportional, which means that the missing side can be found using a rule of three.
x - 10
3 - 6
Applying cross multiplication:
[tex]6x = 30[/tex]
[tex]x = \frac{30}{6} = 5[/tex]
The missing side length is of 5.