Default Swap external sd card to internal memory

First you need an explorer (like Root explorer, Nokia File Explorer, ...)
Then come to this folder: \system\etc\
or root\system\etc\
Then at the bottom you will see one file: "vold.fstab",
plus uh need a file called ""vold.emmc.fstab"" it is not present in nokia X so download it and put it into the same "etc" folder (download links are given below)
Open "Vold.fstab" with "Text Viewer" (the vold.fstab) then roll to bottom you will see something like:
dev_mount sdcard /storage/sdcard0 auto /devices/platform/msm_sdcc.1/mmc_host

dev_mount emmc /storage/sdcard1 21 /devices/platform/msm_sdcc.3/mmc_host/mmc0

Now change the sdcard0 with the sdcard1 then save.

then restart the phone