Sara can finish a work in 18 days and Tara can complete the same work in 15 days. Tara worked for 10 days and left the job. In how many days can Sara finish the remaining work alone?

To find the number of days Sara needs to finish the remaining work, we can analyze the rate of work done by Sara and Tara individually.

First, let us find the work rate of each person per day:
Sara can finish the entire work in 18 days. Thus, Sara's work rate per day is:
$\frac{1}{18}$ of the total work per day.
Tara can finish the entire work in 15 days. Thus, Tara's work rate per day is:
$\frac{1}{15}$ of the total work per day.

Now, let us calculate the amount of work completed by Tara before she left:
Tara worked for 10 days. The work completed by Tara in 10 days is:
$\text{Work done by Tara}=10\times \frac{1}{15}=\frac{10}{15}=\frac{2}{3}$ of the total work.

Next, we determine the remaining portion of the work:
$\text{Remaining work}=1-\frac{2}{3}=\frac{1}{3}$ of the total work.

Finally, we calculate the number of days Sara takes to finish this remaining work alone:
$\text{Time taken by Sara}=\frac{\text{Remaining work}}{\text{Sara's daily rate}}=\frac{\frac{1}{3}}{\frac{1}{18}}$
$\text{Time taken by Sara}=\frac{1}{3}\times 18=6\text{days}$.

Therefore, Sara can finish the remaining work alone in 6 days.