The underlined portion "Una la computadora" is incorrect because it improperly combines two articles in Spanish. "Una" is the indefinite article meaning "a" or "one," and "la" is the definite article meaning "the." In Spanish, you should use either one or the other, not both at the same time.
The correct phrasing would be either "Una computadora" (A computer) if you are introducing it for the first time, or "La computadora" (The computer) if it has already been mentioned or is known in context. So the correct sentence should be either:
- "Una computadora está en mi mochila." (A computer is in my backpack.)
- "La computadora está en mi mochila." (The computer is in my backpack.)