JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" id="A1" value="" placeholder="0"/>
<input type="text" id="B1" value="" placeholder="0"/>
<input type="text" id="1" value="" placeholder="0" onChange="javascript:calcular(this.id);"/>
<input type="text" id="resultado1" value="" readonly/>

<br><br>
<input type="text" id="A2" value="" placeholder="0"/>
<input type="text" id="B2" value="" placeholder="0"/>
<input type="text" id="2" value="" onChange="javascript:calcular(this.id);"/>
<input type="text" id="resultado2" value="" readonly/>

<br><br>
<input type="text" id="A3" value="" placeholder="0"/>
<input type="text" id="B3" value="" placeholder="0"/>
<input type="text" id="3" value="" onChange="javascript:calcular(this.id);"/>
<input type="text" id="resultado3" value="" readonly/>

JavaScript

function calcular(X){
    n1 = document.getElementById(X).value;
   n2 = document.getElementById("A"+X).value;
   n3= document.getElementById("B"+X).value;
   r1= (parseInt(n1)*0.30)+(parseInt(n2)*0.30)+(parseInt(n3)*0.40);
   document.getElementById("resultado"+X).value = r1;

}