Working out the group structure of parent and subsydiary

Hi

I am working a question from the BPP Revision kit and i am struggling to work out the group structure between a parent company and its subsidiary. I need to work out what percentage the parent owns the subsidiary.

In parents individual accounts in the balance sheet under investments i have:

21,000,000 $1 ordinary shares in subsidiary at cost.

The equity section in parent accounts is:
$1 ordinary shares $100,000

The equity section in subsidiary accounts is:
$1 ordinary shares $30,000

Fair value of the non-controlling interest at date of acquisition was $11,800

Apparently the parent owns 70% of the subsidiary but i can not work how, please help?