Hot to make a child element not to inheritance the atributes

Hi,

I have a rule:

p {
margin-left:10%;
margin-right:20%;
}

The wordpress puts the images inside p tags and I have the next code generated

This shrinks the picture too.

I tried
p:not(img){
margin-left:10%;
margin-right:20%;
}

But it does not seems to work.

I put
p > img {
max-width:130%;
}
But is not aligned right.

Thank you.