Let the cost price of the item be \( C \).
- Selling at a loss of 10% means that the selling price \( SP_1 \) is:
\[
SP_1 = C \times \left(1 - \frac{10}{100}\right) = C \times 0.90
\]
- If the item was sold for ₹120 more, the new selling price \( SP_2 \) would be:
\[
SP_2 = SP_1 + 120 = C \times 0.90 + 120
\]
- Selling at a gain of 5% means that the new selling price \( SP_2 \) is also:
\[
SP_2 = C \times \left(1 + \frac{5}{100}\right) = C \times 1.05
\]
Now, equating the two expressions for \( SP_2 \):
\[
C \times 0.90 + 120 = C \times 1.05
\]
Solving for \( C \):
\[
120 = C \times 1.05 - C \times 0.90
\]
\[
120 = C \times (1.05 - 0.90)
\]
\[
120 = C \times 0.15
\]
\[
C = \frac{120}{0.15} = 800
\]
Thus, the cost price of the item is ₹800.