Answer:
12
Step-by-step explanation:
This is a proportion question.
8/x = 12/(12 + 6)
8/x = 12/18 Reduce the right hand side
8/x = 2/3 Cross multiply
2x = 8*3 Combine the right side
2x = 24 Divide by 2
x = 24/2
x = 12