"The fox has a mouse."
Translation:여우가 쥐를 가지고 있어요.
Some of us do need to learn using the app instead of the website, and so have no access to the tips and tricks lightbulb. It would be nice if Duolingo could rearrange the order in which new words/concepts like this come up, so that we can encounter it using a different learning method first - especially if it's not given as a hint with the underlined words. This is not the first time that I've lost health on a concept I could not guess, but that doesn't make it any less frustrating.
(Keep in mind I am still learning Korean, but bc I studied elsewhere before encountering this lesson I have run into this concept before) 있다 more literally means "to exist". This is why 저는 언니가 있어요 literally means "In my case/as for me, an older sister exists", and 가 is used instead of 를 Here 가지다 means to possess, which is why 쥐 has the object marking particle 를 attached, because the mouse isn't doing anything. It's an object being acted upon. It's just that the literal translation of 있다 can sound awkward in English so it gets translated as "to have". 있다 I think sounds less possesive than 가지다