Given details are,
Selling price of book is = Rs 258
The man’* gain percent is = 20% of 100 = 20/100
So, let us consider the cost price of book be Rs x
By solving,
x + x×20/100 = 258
x + x/5 = 258
(5x+x)/5 = 258
By cross multiplying
6x= 5×258
x = 1290/6
= 215
Now, the cost price of book is = Rs 215
For a gain of 30% the man should sell the book at = 215 + 215×30/100
= 215 + 64.5
= 279.50
∴ To gain 30% the man should sell the book at Rs 279.50.
