JSFiddle - React, Tailwind, and code Playground

HTML

<select id="old" name="i_have">
                <option value = "select_option">Select Option</option>
                <option value = "three_compact">3 Compact</option>
                <option value = "three_regular">3 Regular</option>
                <option value = "three_triple">3 Triple</option>
                <option value = "five_compact">5 Compact</option>
                <option value = "five_regular">5 Regular</option>
                <option value = "five_triple">5 Triple</option>
                <option value = "seven_compact">7 Compact</option>
                <option value = "seven_regular">7 Regular</option>
                <option value = "seven_triple">7 Triple</option>
                <option value = "nine_compact">9 Compact</option>
                <option value = "nine_regular">9 Regular</option>
                <option value = "nine_triple">9 Triple</option>
            </select>
            <select id="new" name="i_want">
                <option value = "select_option">Select Option</option>
                <option value = "three_compact">3 Compact</option>
                <option value = "three_regular">3 Regular</option>
                <option value = "three_triple">3 Triple</option>
                <option value = "five_compact">5 Compact</option>
                <option value = "five_regular">5 Regular</option>
                <option value = "five_triple">5 Triple</option>
                <option value = "seven_compact">7 Compact</option>
                <option value = "seven_regular">7 Regular</option>
                <option value = "seven_triple">7 Triple</option>
                <option value = "nine_compact">9 Compact</option>
                <option value = "nine_regular">9 Regular</option>
                <option value = "nine_triple">9 Triple</option>
            </select>
            <div id="results">
            </div>
            </div>

JavaScript

$("#old, #new").change(function(){
	var old = $("#old").val(),
  	newval = $("#new").val();
  
  if(old=='three_compact' && newval=='five_compact'){
		$("#results").text('10');
 	}
  /* REST OF IF-ELSE CONDITIONS */
});