It is not possible to delete/remove the unneeded built-in, Apple provided iOS apps from a device running iOS 9 or earlier.
In iOS 10, it became possible to remove a selection of Apple's built-in apps, but only from the Springboard (Home screen). The apps weren't really removed from the device, but simply hidden from view (thereby reducing clutter). They continue to persist on device, thereby consuming storage space. (Technically, this was due to the reason iOS 10 was built. Apple's built-in apps were part of the iOS itself, rather than installable from the App Store).
Starting with iOS 11, Apple changed the way it built iOS and shipped first party apps such that it finally became possible to fully delete a selection of built-in apps and reclaim the storage space occupied by them. The same can be installed later from the App Store if need be.
For more information, refer to the helpful support article from Apple, Remove built-in Apple apps from the Home screen on your iOS 10 device or Apple Watch