價格：免費
檔案大小：104.2 MB
版本需求：需要 iOS 7.0 或以上版本。與 iPhone、iPad 及 iPod touch 相容。
支援語言：英語
Improve yore math skills in mental arithmetics subtraction!
You will always practice at the right level. If you are quick and answer right, you will reach a higher level quickly.
The numbers of levels are unlimited!
This app is suitable for all ages.
支援平台：iPhone, iPad