How to display only two buttons when radio button is checked?

I have 3 buttons option for my form, but 2 only is display 1 is hidden. I want to change those display depend on radio button input. here is my html code:

<label for="pay">Payment Option</label>
      <div class="row check">
        <div class="col-sm-6">          
          <input type="radio" id="gcash" name="pay" value="gcash" checked="checked"/>
          <label for="gcash" class="pay">Gcash</label>
        </div>
        <div class="col-sm-6">
          <input type="radio" id="walk" name="pay" value="unpaid"/>
          <label for="walk" class="pay">Walk In</label>
        </div>
 </div>

<div class="buttons">
      <a href="#" class="res-btn" role="button">Back</a>
      <a href="#" class="res-btn" role="button">Proceed payment</a>
      <input type="submit" class="res-btn hidden" name="btn-submit" value="Submit">
</div>

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