Image is not being centered in the posts

Hi there seems to be a css issue.
These margin settings around line 15 of your style.css file:

.single .post_content h2.entry_title {
    font-size: 3.2em;
    line-height: 42px;
    margin-top: 80px;
    text-transform: capitalize;
}

seems to be overriding these:

img.centered, .aligncenter {
    display: block;
    margin: 0 auto 10px;
}

disable the upper one and you should be good to go.And remember to do all the changes in the child theme style.css file and not directly in the parent theme style.css.

Sorry the upper line code is this one :

#content .post img, #content .page img {
    border: 1px solid #F8F8F8;
    margin: 0 10px 10px 0;
    max-width: 100%;
    padding: 0;
}