Answer:
Number of apple in basket = 2
Number of banana in basket = 5
After that, some additional apples and bananas were added in basket.
and the ratio of number of apple and banana becomes

It means that the number of banana is just double the number of apples.
This can be possible in many ways.
One of the possible ways is 1 apple is added in basket
and 1 banana is added in basket.
So, total number of apple in basket = 3
and total number of banana in basket = 6
Thus, ratio will become
.
Hence, one apple will be added in basket.