Translation:There is a funny woman in this picture.
This is what's great about Arabic; as you progress in the language, you'll start to get more familiar with the templates that the roots fall into. This particular one is the adjective for verbs in Form IV – causative verbs which use the template aCCaCa. In this case, the verb is "أَضحَكَ" (aDH7aka – to make laugh). The active participle, which is used for the adjective too, uses the template muCCiC – so, here, it's "مُضحِك" (muDH7ik – s.o./sth. that makes (s.o.) laugh), and then of course with ta' marbuta, as it's the feminine form (مُضحِكة - muDH7ika).
For further reference, a couple other verbs and their participles are:
"أَحزَنَ" (a7zana – to sadden)
"مُحزِن" (mu7zin – sad; saddening)
"أَزعَجَ" (az3aja – to annoy)
"مُزعِج" (muz3ij – annoying)
"أَفرَحَ" (afra7a – to delight s.o.)
"مُفرِح" (mufri7 – delightful)
You have a good question! The "t" sound comes from ة ta marbuTa. So, the audio pronounces the sentence above something like this:
فِي هذه الصورةِ امرأة
"fii haadhihiS Suuratimra2a"
We assume that Duolingo tries to omit sound at almost all words and doesn't follow Standard Grammar as people oftentimes do on their daily basis.
"Normally", it is pronounced something like follows: "fii haadhih 2aS-Surah 2imra-2ah". But, Duolingo wants to keep the pronunciation flowing.
So, the "t" sound from ة is raised.
Whilst, the ا in امرأة is neglected, like when they say "ما اسمك؟" : what's your name?
Hence, it becomes "tim".
(For Standar Grammar, the explanation will be different).
Nb: if we follow Standard Arabic, the correct pronunciation for هذه is هَذه hadhihi -- without dagger alif.