Let x = "cost price". From the condition, we know that Kunal (I write it intently with the capital K, since I suppose it is the name of the person) sold it for 0.9x rupees. Again, from the condition, we know that 0.9x + 60 = x*(1+0.05). It is your equation to solve. 0.9x + 60 = 1.05x ====> 60 = 1.05x - 0.9x ====> 0.15x = 60 ====> x == 400 rupees. Answer. The cost price of the shirt is Rs 400.