
In Spanish, the "ir a + infinitive pattern" corresponds to "el futuro próximo." In English, this translates to "near future" and is similar to the "be going to + infinitive pattern." It is used to indicate an action that is going to happen soon.
Remember that the verb "ir," which is an irregular verb, has to be conjugated in the present tense:
IR
Yo voy
Tú vas
Él / ella / usted va
Nosotros / nosotras vamos
Vosotros / vosotras vais
Ellos / ellas / ustedes van

Now, let's pay attention to the subject of the given sentence:
Ellos ___ a estudiar.
The subject is obviously "ellos," which is the masculine form of "they" in Spanish.

Therefore, our answer is:
Ellos van a estudiar Español.
Translation: They are going to study Spanish.