<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<table class="table table-bordered" style="vertical-align:middle;width:500px;">
<td style="width:80%">
<table class="table table-bordered">
<thead>
<tr>
<th>Month</th>
<th>Savings</th>
<th>Savings for holiday!</th>
</tr>
</thead>
<tbody>
<tr>
<td colspan="2" style="background-color:#ddd">
<table>
<tr>
<td>January</td>
<td>$100</td>
</tr>
<tr>
<td>February</td>
<td>$80</td>
</tr>
<tr>
<td>February</td>
<td>$80</td>
</tr>
</table>
</td>
<td>
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</td>
</tr>
