Answer:
Carlos has practiced piano for  hours.
 hours.
Carlos needs to practice  hours.
 hours.
Step-by-step explanation:
We have been given that Carlos wants to practice piano 2 hours each day. He practices piano for 3/4 hour before school and 7/10 hour when he gets home. 
First of all, we will find piano practiced before school and after school by adding both amounts as:

Make a common denominator:


Add numerators:

 
  
Therefore, Carlos has practiced piano for  hours.
 hours.
Now, we will subtract  from 2 find number of hours Carlos needs to practice to reach his goal.
 from 2 find number of hours Carlos needs to practice to reach his goal.





Therefore, Carlos needs to practice  hours before going to bed in order to meet his goal.
 hours before going to bed in order to meet his goal.