You have to set the value of those inputs to custom states. That way you can have one input that is the SUM of all the custom states and each other input just displays the Number from its corresponding custom state. Also the input’s displayed value will change/update as your calculations update the custom states.
How about using input boxes rather than text boxes (just style them to look how you want and select ‘this input is disabled’). No need for custom states or math js etc. then.