I'm going to assume that the question should say “at a profit of 5%”.
Restate question in the form of a equation.
Let C = the cost price of the item.
C + 0.705 C = C - 0.05 C + Rs 50
0.05 C = - 0.05 C + Rs 50
0.10 C = Rs 50
C = Rs 500
The cost price of the item is Rs 500
I hope this help you