1. open file /public_html/storefront/controller/blocks/order_summary.php
2. go to line #86
3. replace 'price' => $this->currency->format($this->tax->calculate($result['price'], $result['tax_class_id'], $this->config->get('config_tax'))),
with
'price' => $this->currency->format($this->tax->calculate($result['price'], $result['tax_class_id'], $this->config->get('config_tax'))*$result['quantity']),