Answer:
Part A) The rate is

Part B) In 1 year the tree grows 3 feet
Explanation:
Part A) write the rate at which this tree grows as a fractions
we know that
To find out the rate at which the tree grows divide 1/4 foot by 1/12 year
so

Part B) how many feet does the tree grow in 1 year?
we know that
The tree grows at rate of

Simplify

That means ----> The tree grows 3 ft in 1 year
therefore
In 1 year the tree grows 3 feet