I do not know if it's the best way, but it might solve your problem!
link
<form>
<label for="placa">Placa:</label>
<input type="text" class="placa">
<label for="concessionaria">Concessionaria:</label>
<input type="text" name="concessionaria" id="concessionaria">
</form>
<form>
<label for="placa">Placa:</label>
<input type="text" class="placa">
<label for="concessionaria">Concessionaria:</label>
<input type="text" name="concessionaria" id="concessionaria">
</form>
<form>
<label for="placa">Placa:</label>
<input type="text" class="placa">
<label for="concessionaria">Concessionaria:</label>
<input type="text" name="concessionaria" id="concessionaria">
</form>
javascript:
$(".placa").on('input', function() {
$(this).parent().find('#concessionaria').val($(this).val());
});