The ratio 6:3 simplifies to 2:1 when you divide both sides by 3. This means for every 2 of one item (6) there is 1 of another item (3).
From the options given, the correct description that represents the ratio 6:3 is:
6 triangles to 3 circles
This indicates that for every 6 triangles, there are 3 circles, which matches the ratio of 6:3.