Hello, @TFS,
Cart is the default WC page, all available settings you can find in WooCommerce > Settings.
Also, you can use custom CSS code, Please copy and paste the below-given CSS code to XStore >> Theme Settings >> Theme Custom CSS >> Global CSS and check back your site after clearing the browser cache,
.woocommerce-cart .col-md-5.cart-order-details,
.woocommerce-cart .col-md-7 {
width: 100%;
}
Under Private Content Area:
Regards 8Themes Team.