Learn Turkish: Sınavda yedinci soruyu yanlış cevapladım. - I answered the seventh question wrong in the exam.

The suffix for ordinal numbers (like the English '-th') is indeed -ıncı, -inci, -uncu, or -üncü depending on vowel harmony. However, because yedi (seven) already ends in a vowel, the starting vowel of the suffix is dropped to avoid having two vowels right next to each other. This makes it yedinci instead of yediinci.

Why does soru have the suffix -yu attached to it?

soruyu is in the accusative case, which is used to mark a specific direct object. Because you are talking about a very specific question (the seventh question), you must add the accusative suffix -u. The y is a buffer letter used to smoothly separate the two vowels (soru-y-u).

How is the verb cevapladım formed?

The root of this word is actually the noun cevap (answer). In Turkish, you can often turn a noun into a verb by adding the suffix -la or -le. Here, cevap becomes cevaplamak (to answer). From there, we add the past tense suffix -dı and the first-person ending -m (I).

Why is yanlış placed right before the verb?