How to give parent opacity but not effect in child

How to give parent opacity but not effect in child

it's very simple now you can used to RGBA format
r=red
g=green
b=blue
a=alpha

EXAMPLE

HTML

<div class="parent">
<p>
Give to parent opacity but not effect in child
</p>
</div>

CSS

.parent{
background:rgba(0,0,0,0.2);
}

Live Demo

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