I can answer the first one.
Just do 3150/1000
Mutiply by 4 for rabits and 2 for chickens
(1) let "r" denote number of rabbits, "c" number of chickens
Set up the equations:
Answer: There are 575 rabbits and 425 chickens
(2) m - number of Mike's stamps, a - number of Andrew's stamps.
Set up equations:
Answer: Mike has 48 stamps. Andrew has 12 stamps.