Answer: 2 triangles to 5 circles or 2:5
In order to find the simplest ratio, we must find a number that both of our numbers can be divided by. Our starting ratio is 6:15. Both numbers can be divided by 3. So our equation will look like this
6/3 : 15/3
6 divided by 3 is 2 and 15 divided 3 is 5.
This means our new ratio is 2:5
2 and 5 can do not have a number that both can be divided by which means our simplest ratio is 2 triangles to 5 circles or 2:5
I hope this helped & Good Luck <3 !!!