Answer
There were 15 oranges initially.
There were 45 apples initially.
Hence, there were (15 + 45) = 60 fruits there initially.
Step-by-step explanation
Let the number of oranges be x
Let the number of apples be y
The ratio of the number of oranges to the number of apples is 1 : 3 implies:
If 21 oranges were added and the ratio became 4 : 5, this implies:
To know how many fruits were there initially, solve the system of the equations:
x = 15 implies there were 15 oranges initially.
To get y, substitute x = 15 into equation (i):
y = 45 implies there were 45 apples initially.
Hence, there were (15 + 45) = 60 fruits there initially.