If the cost price of 10 articles is equal to the selling price of 7 articles, then the gain or loss percent is = ?

According to the question,
10 Cost Price = 7 Selling Price
$$\eqalign{ & \frac{{{\text{CP}}}}{{{\text{SP}}}} = \left. {\frac{7}{{10}}} \right\rangle {\text{3 unit profit}} \cr & {\text{Profit}}\% = \frac{3}{7} \times 100 \cr & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\, = 42\frac{6}{7}\% {\text{ gain}} \cr} $$