accounts plz help

Invoce Price=200000*25%=250000 (1/5 on invoce price so 1/4 on cost)

Ordinary Commission=250000*3%=7500...............................(a)

Other commission is on= Actual Sale Price -invoice price -ordinary commission-octroi

                                            300000(225000/.75)-250000=50000-7500-5000(octroi)=37500

so extra commission is 10%  therefore 37500 is 90% then what is 10%=37500*90/10=4167..............(b)

7500+4167=11667

good reply by HEMANSHU