You might need a calculator for this one
[1]+[2]+[3] = 12
[2]+[3]+[4] = 14
[3]+[4]+[5] = 14
[4]+[5]+[1] = 11
[5]+[1]+[2] = 12
What is [8]?
Why not visit https://www.facebook.com/elliottlinepuzzles/ where you'll be able to send me your solution, and I'll let you know if you're correct.
Update: solution now in comments