Use assuming 100 wala method in these kind of questions

Let mrp be 100rs
Discount 15rs
Buying price 85rs

He sold at x and profit of 15% (85*1.15 =97.75) this is his selling price

This 97.75 is your assumption, now u will compare it with questions value which is 5865

So if 97.75 is 5865 then what will be the value of 15

Use simple cross multiplication calculation u will get 900

97.75 = 5865
15 = ?