Question

Tell what the following people are going to do tomorrow, by changing the present tense verb to the correct form of the future tense. Tú practicas el piano.

Answer 1

Present: Tu practicas el Piano 
Future: Tu vas a practicar el piano

Answer 2

Since you're asking about the future tense, I'm assuming that you need the verb prácticas in future tense. Here are are the ways its conjugated

Yo practicaré
Tú practicarás
El/ella/usd practicará
Nosotros practicaremos
Vosotros practicaréis
Ellos/ellas/usds practicarán
So it would be

Tú practicarás el piano
I hope this is helpful! The endings come after the -ar, and keep in mind this only works for ar verbs.