how can i display a feild the value of it is add or subtract to field
Use ClientEvents in Add/Edit Page Field Properties to do your calculation; you should see sample code when you double-click on the code list on the left panel; or use Page Design to do your calculations.
Do you have any sample video?
Table Field Calculations in RadSystems Studio | Lowcode - YouTube and this PHPRad Tips and Tricks 6: How to use the Page Events properly - Part 1 - YouTube is similar to Radsystems Studio.
Always search for tutorials on YouTube or subscribe to Radsystem’s YouTube channel or other channels that provide tutorials on Radsystems Studio. Most videos contain solutions you might need.