Kyle has a third of Fabian's number of marbles, so he has 15 / 3 = <<15/3=5>>5 marbles.

Miles has a fifth of Fabian's number of marbles, so he has 15 / 5 = <<15/5=3>>3 marbles.

Miles and Kyle together have 5 + 3 = <<5+3=8>>8 marbles.

# Answer

8
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Fabian has three times more marbles than Kyle and five times more than Miles. If Fabian has 15 marbles, how many marbles do Kyle and Miles have together?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
8
Fabian has three times more marbles than Kyle and five times more than Miles. If Fabian has 15 marbles, how many marbles do Kyle and Miles have together?
train