Question

On selling a sofaset on rs21600, a dealer gains 8%. For how much did he get

Answer 1

We simply must solve 
21600 + 21600*8/100
here we would get the second term to be the money gained and hence the first term is added to find at what cost he sold 
so by solving
21600 + 1728
23328

so he gains 1728
by selling at 23328