Tanvy bought a watch for Rs 1980 including VAT at 10%.

Let the original price of the watch be Rs x.

VAT = 10% of Rs x

$=\mathrm{Rs} \quad\left(x \times \frac{10}{100}\right)$

$=\mathrm{Rs} \frac{10 x}{100}$

$\therefore$ Price including VAT $=\mathrm{Rs}\left(x+\frac{x}{10}\right)$

$=\operatorname{Rs} \frac{11 x}{10}$

Now, $\frac{11 x}{10}=1980$

$\Rightarrow x=\left(1980 \times \frac{10}{11}\right)$

= 1800

Hence, the original price of the watch is Rs 1,800.