Lily planted 9-3 = <<9-3=6>>6 apple trees in her backyard.

They planted 9+6 = <<9+6=15>>15 apple trees in their backyards collectively.

# Answer

15
<|im_start|>system
You are a helpful assistant.<|im_end|>
<|im_start|>user
Ava planted 9 apple trees in her backyard. That's 3 more than Lily planted in her backyard. How many apple trees did they plant in their backyards collectively?
Please reason step by step, and put your final answer within \boxed{{}}.<|im_end|>
<|im_start|>assistant

user
15
Ava planted 9 apple trees in her backyard. That's 3 more than Lily planted in her backyard. How many apple trees did they plant in their backyards collectively?
train