Below is an instruction that describes a task. Write a response that appropriately completes the request in English. Please answer in English.

### Instruction:
Andrew works in a company that provides a generous vacation allotment: for every 10 days worked, you get 1 vacation day. If last year Andrew worked 300 days and took 5 days off in March and twice as many in September, how many more vacation days can Andrew still take?

### Response:
If for every 10 days worked Andrew earns 1 day of vacation, then over 300 days worked he would have earned 300/10=<<300/10=30>>30 days of vacation
We know that in March Andrew used 5 days of vacation, and that in September he used twice as many. That means in September Andrew used 5*2=<<5*2=10>>10 days of vacation.
In total, Andrew has used 5 vacation days in March and another 10 in September. Therefore, Andrew has used 5+10=<<5+10=15>>15 vacation days.
If Andrew earned 30 days of vacation but has only used 15, then he can still take another 30-15=<<30-15=15>>15 days off.
#### 15