For 1-6, all you have to do is conjugate the words by taking away the -ar at the end of the infinitive and adding the designated ending.
1. cantar, canto, cantas, canta, cantamos, cantan
2. preguntar, pregunto, preguntas, pregunta, preguntamos, preguntan
3. contestar, contesto, contestas, contesta, contestamos, contestan
4. practicar, practico, practicas, practica, practicamos, practican
5. desear, deseo, deseas, desea, deseamos, desean
6. llevar, llevo, llevas, lleva, llevamos, llevan
section two conjugate the infinitive like before, with the subject from the sentence
1. viajan
2. hablamos
3. llegan
4.dibujo
5. compra
6. regresan
7. termina (i think)
8. buscas
Yes It is correct your doing great ^-^
Gauchos, caballos, carne asada
The correct answer would be abrió.
Usted <u>abrió</u> la ventana.
You (formal) opened the window.
Hope this helps! :3