How do I remove specific styles from the parent theme css using the child theme css?

The only way to “remove” styles from the parent theme is to override them in your child theme’s css.

For example if you have the following declaration in your parent theme:

.someclass{
    width: 200px;
    float: left;
 }

You can override the width and float by declaring the following in your child theme:

.someclass{
    width: auto;
    float: none;
}