JSFiddle - React, Tailwind, and code Playground

HTML

<form>
<h1>Fare Calculator</h1>
    <h2>Select Embarkation/Debarkation Point</h2>
<select id="bild" onchange="bBild()">
   <option class="GUADALUPE" value="0">Guadalupe</option>
    
    <option class="PINAGBUHATAN" value="0">Pinagbuhatan</option>
  <option class="SAN JOAQUIN" value="0">San Joaquin</option>
  <option class="STA. ANA" value="0" selected>Sta. Ana</option>
  <option class="PUP" value="0">PUP</option>  
  <option class="ESCOLTA" value="0">Escolta</option>
  <option class="INTRAMUROS" value="0">Intramuros</option>
 
</select>
<select id="bio" onchange="bBio()">
     <option class="GUADALUPE" value="0">Guadalupe</option>
  <option class="PINAGBUHATAN" value="45">Pinagbuhatan</option>
  <option class="SAN JOAQUIN" value="18">San Joaquin</option>
  <option class="STA. ANA " value="20" selected>Sta. Ana</option>
  <option class="PUP" value="50">PUP</option>  
  <option class="ESCOLTA" value="50">Escolta</option>
  <option class="INTRAMUROS" value="50">Intramuros</option>

</select>
<input type="button" value="Calculate" onClick="GetSelectedItem();">
</form>

JavaScript

function bBio()
{
    var bio = document.getElementById("bio");
    var biobetyg = parseFloat(bio.options[bio.selectedIndex].value);
    return biobetyg;
    }

function bBild()
{
var bild = document.getElementById("bild");
    var bildbetyg = parseFloat(bild.options[bild.selectedIndex].value);
    return bildbetyg;
    
}

function GetSelectedItem()
{
    var merit = bBio() + bBild();
    var strSel = "The Value is: " + merit ;
    alert(strSel);
}