How to eliminate partition of storage without rooting?

[AC Question]

Hi All... So I have a sansui lifepad running kitkat it has three storage divisions - "internal storage" default download location for apps ; "USB Storage" also internal but only seems to support media files; "sd card" external micro sd seems to support the move to sd card function and media when transferring from pc to phone. I figure the "Usb storage must be a partition of the total internal storage so how do I rejoin these two partitions as to be able to download more apps without rooting my tab?