Pls explain the question with the ans - Maths - Data Handling

Question

Pls explain the question with the ans

Rahul K · Accepted Answer

Dear student, Let the cost price 100 With 20% profit, selling price
= 100 + (20/100)*100 = 120 Now if he purchase at 20% discount,
Second cost price = 100 - 20 = 80 At the end he gain 25% Second
selling price = 80*(125/100) = 100 Difference between selling price
= 120-100 =20 If the difference is Rs 20, C P = 100 If the
difference is Rs 60, C P = (100/20)* 60 = 300 Hence, Cost price of
the book is Rs 300 Regards

Pls explain ..... the question with the ans