JSFiddle - React, Tailwind, and code Playground

HTML

<input type="text" value="10" id="text">

<input type="checkbox" id="check" value="1" onClick="if(this.value == '1'){this.value='101'}else{this.value='1'}">
<label for="check">101</label>
<input type="checkbox" id="check2" value="1" onClick="if(this.value == '1'){this.value='11'}else{this.value='1'}">
<label for="check">11</label>

<input type="text" value="" id="end">

<input type="button" value="считаем" onClick="var a1=document.getElementById('text').value;
var a2=document.getElementById('check').value;
var a3=document.getElementById('check2').value;
document.getElementById('end').value = a1*a2*a3;">

CSS

#end {border-width: 0px;
color: red;
}