Question 772663
That is 300 Rs minus 10% of 300 Rs and 100 Rs plus 10% of 100 Rs.  
In plain number symbols, {{{-0.1*300+0.1*100=-30+10=-20}}}


Loss of {{{(20/400)*100=(1/20)*100=5}}}
This is "loss", because the value is negative  (see the -20).
This is 5% loss.