JSFiddle - React, Tailwind, and code Playground

HTML

<label>loan</label>
<input type="text" name="loan_price" id="loan_price" value="4900"><br>

<label>first payment in %</label>
<input type="text" name="charge" id="charge"><br>

<label>first payment $$$</label>
<input type="text" name="first_payment_amount" id="first_payment_amount"><br>

<label>max loan</label>
<input type="text" name="loan" id="loan"><br>

JavaScript

var $price      = $("input[id='loan_price']"),
    $percentage = $("input[id='charge']").on("input", calculatePrice),
    $discount   = $("input[id='loan']").on("input", calculatePerc),
	$discount2   = $("input[id='charge']").on("input", calculatePrice2);
	$discount3   = $("input[id='first_payment_amount']").on("input", calculatePrice3);
    

function calculatePrice() {
    var percentage = $(this).val();
    var price      = $price.val();
    var calcPrice  = (price - ( price * percentage / 100 )).toFixed(2);
    $discount.val( calcPrice );
}

function calculatePerc() {
    var discount = $(this).val();
    var price    = $price.val();
    var calcPerc = 100 - (discount * 100 / price).toFixed(2);
    $percentage.val( calcPerc );
	
	var firstPayment = (price - discount).toFixed(2);
	var discount2 = document.getElementById('first_payment_amount');
	discount2.value = firstPayment;	
}

function calculatePrice2() {
    var price    = $price.val();
	var discount    = $discount.val();
    var calcPrice  = (price - discount).toFixed(2);
    //$discount2.val( calcPrice );
	var discount2 = document.getElementById('first_payment_amount');
	discount2.value = calcPrice;
}

function calculatePrice3() {
    var price    = $price.val();
	var discount3    = $("input[id='first_payment_amount']").val();
    var calcPrice  = ((discount3/price)*100).toFixed(2);
	
	var toBank = (price - discount3).toFixed(2);
	//alert(calcPrice);
    //$discount2.val( calcPrice );
	var percentage = document.getElementById('charge');
	percentage.value = calcPrice;
	
	var discount = document.getElementById('loan');
	discount.value = toBank;	
}


var $price1      = $("input[id='loan_price']"),
	$fPay1      = $("input[id='first_payment_amount']"),
    $percentage1 = $("input[id='commission_in_percent']").on("input", cPrice),
    $discount1   = $("input[id='commission']").on("input", cPerc);
    

function cPrice() {
    var percentage1 = $(this).val();
    var price1      = $price1.val();
	var fPay1 =...