# Help with a commerce app **URL:** \ **Category:** Questions about Thunkable X\ **Created:** [March 27, 2020, 9:15am UTC](https://community.thunkable.com/t/help-with-a-commerce-app/538530 "2020-03-27T09:15:15Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![anonimo112233445544w](https://avatars.discourse-cdn.com/v4/letter/a/9fc348/32.png) [@anonimo112233445544w](https://community.thunkable.com/u/anonimo112233445544w)\ **Post date:** [March 27, 2020, 9:15am UTC](https://community.thunkable.com/t/help-with-a-commerce-app/538530/1 "2020-03-27T09:15:16Z")
I need some help with a commerce app that I am working on. The app the I am talking about is an app that saves all the debts you have with your friends. For example if you owe 20 dollars to one of your friends it will save it and remind it to you but then if he gives you back 10 the app needs to know that he still needs to give you 10 more. It is like the money pie bot in telegram. To do this I created a database in Firebase to save all information necessary. But I don´t know how to interact with the database to take those numbers and interact with them, adding and subtracting. Also I need to create an additional list that just shows the money you owe and the money they owe you. If someone wants to help I can give him my Discord or Skype. ---
**Author:** ![jared](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/jared/32/138473_2.png) [@jared](https://community.thunkable.com/u/jared)\ **Post date:** [March 27, 2020, 10:57am UTC](https://community.thunkable.com/t/help-with-a-commerce-app/538530/2 "2020-03-27T10:57:59Z")
Are you unable to do math eith values you have stored to Firebase? ---
**Author:** ![anonimo112233445544w](https://avatars.discourse-cdn.com/v4/letter/a/9fc348/32.png) [@anonimo112233445544w](https://community.thunkable.com/u/anonimo112233445544w)\ **Post date:** [March 30, 2020, 12:02pm UTC](https://community.thunkable.com/t/help-with-a-commerce-app/538530/3 "2020-03-30T12:02:47Z")
I don’t know how to take those values out of the database and subtract and add new values. For example if I have a value of 20 in the database, I don’t know how to take that value out so it can be modified with the new information that is put into. ---
**Author:** ![jared](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/jared/32/138473_2.png) [@jared](https://community.thunkable.com/u/jared)\ **Post date:** [March 30, 2020, 12:04pm UTC](https://community.thunkable.com/t/help-with-a-commerce-app/538530/4 "2020-03-30T12:04:31Z")
to interact with data stored in firebase depends on how it is stored. can you show an example of a data tree? the easy answer is to GET the value from a particular key or key add to it save it back to the same place right? ---
**Author:** ![ioannis](https://sea1.discourse-cdn.com/flex015/user_avatar/community.thunkable.com/ioannis/32/146956_2.png) [@ioannis](https://community.thunkable.com/u/ioannis)\ **Post date:** [November 8, 2024, 11:29am UTC](https://community.thunkable.com/t/help-with-a-commerce-app/538530/5 "2024-11-08T11:29:58Z")