Kelly's art teacher asked him to draw a rectangle with a length of $6$ inches and a width of $10$ inches.  After Kelly does so, his teacher changes her mind and asks him to draw a proportional rectangle that has a length of $9$ inches.  How many inches wide is the new rectangle?
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Kelly's art teacher asked him to draw a rectangle with a length of $6$ inches and a width of $10$ inches.  After Kelly does so, his teacher changes her mind and asks him to draw a proportional rectangle that has a length of $9$ inches.  How many inches wide is the new rectangle?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
15
Kelly's art teacher asked him to draw a rectangle with a length of $6$ inches and a width of $10$ inches.  After Kelly does so, his teacher changes her mind and asks him to draw a proportional rectangle that has a length of $9$ inches.  How many inches wide is the new rectangle?
train