How do i go about filing removal of condition for my kid who turnes 18yrs

[rosaline 8]

How do I go about filing removal of conditonal greencard for my kid who turned eighteen

[HeatDeath 430]

http://www.uscis.gov/files/form/i-751instr.pdf

Page 1 - Who may file:

You list their name and A# in Part 5 of your own I-751, and their conditions are removed with yours.

Even if they've turned 18, their status is still derivative from yours, so their conditions get removed with yours.

If they got their GC more than 90 days after yours, or if you were dead, they would do their own I-751s, but since you're [presumably] alive and their status is [presumably] derivative from yours, they get included in your I-751. You'll need to include an extra $85 biometric fee for each dependant child that is removing conditions on your I-751, but the $505 I-751 fee covers all of you.

The instructions explain it fairly clearly.