LoveProject

const inputOutput = document.getElementById('usd');

const value = (input.value * 73.84).toFixed(5) + ' $';
inputResult.value = value;
inputOutput.textContent = value;

<div id="out"></div>
<input type="number"  id="Rub" >                
<input type="text" id="Usd">
<script>
  const div = document.getElementById("out");
  const input = document.getElementById("Rub");
  const inputResult = document.getElementById("Usd");
  input.addEventListener("keyup", function() {
    inputResult.value = (input.value * 73.84)toFixed(5) + ' $';
    out.innerText = (input.value * 73.84)toFixed(5) + ' $';
  });
</script>