You manage subscriptions within the Play Store app.
1. Open the Play Store.
2. Tap Account from the drop down in the top left.
3. Tap Subscriptions.
4. Look for the Solitaire Premium subscription and tap on it.
5. Tap "Cancel".
Look under Your Subscription to see your current term and expiration date.
To change your subscription term, choose a new term under Renewal Options.
To stop your subscription, turn off Automatic Renewal under Renewal Options. To avoid being billed for another term, you must turn off automatic renewal at least 24 hours before the end of the current subscription period.