Dog diets

This task is about solving maths problems with rate.

a) An overweight dog was put on limited food and increased exercise to reduce its weight.
The dog lost weight at the rate of 0.4 kg per week.
 
  i)
If it weighed 21.0 kg before the diet how much did it weigh after 12 weeks?
 

__________ kg
 

  ii)
If the goal for the dog's weight was 15.0 kg, how many weeks altogether would it take to reach this (if it lost weight at 0.4 kg per week)?
 

__________ weeks
 

b)
Another dog was put on the same programme. Its weight dropped from 24.0 kg to 18.4 kg in eight weeks. At what rate did this dog lose weight?
 

__________ kg per week