new salary after increase = rs. 9936

let x be the initial salary

initial salary + 15% of initial salary = new salary

x+15%(x)=9936

x+(15/100)(x)=9936

x+(3/20)(x)=9936

x+3x/20=9936

(20x+3x)/20=9936

23x=9936*20

23x=198720

x=198720/23

x=8640

rs. 8640 was his initial salary.

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