From the Emmet Cheat Sheet:
p.class1.class2.class3 <p class="class1 class2 class3"></p>
So, div.row.placeholders will give you:
<div class="row placeholders"></div>
From the Emmet Cheat Sheet:
p.class1.class2.class3 <p class="class1 class2 class3"></p>
So, div.row.placeholders will give you:
<div class="row placeholders"></div>