To find the fraction of photos taken in each continent, we need to divide the number of photos taken in each continent by the total number of photos taken.

The total number of photos taken is 30.

The number of photos taken in Asia is 12.

The fraction of photos taken in Asia is 12/30, which can be simplified to 2/5.

The number of photos taken in Europe is 10.

The fraction of photos taken in Europe is 10/30, which can be simplified to 1/3.

The number of photos taken in Oceania is 5.

The fraction of photos taken in Oceania is 5/30, which can be simplified to 1/6.

The number of photos taken in America is 3.

The fraction of photos taken in America is 3/30, which can be simplified to 1/10.

Therefore, the fractions of photos taken in each continent are:

Asia: 2/5 Europe: 1/3 Oceania: 1/6 America: 1/10