Rohit donated $\frac{1}{5}$ of his monthly income to an non-government organisation (ngo) working for education of girl child,spent 1/4 of his salary on food $\frac{1}{3}$ on the rent and $\frac{1}{15}$ on other expenses .he is left with Rs 9000

Given: Rohit donated $\frac{1}{5}$ of his monthly income to an non-government organisation

He spent $\frac{1}{4}$ of his salary on food ,$\frac{1}{3}$ on the rent and $\frac{1}{15}$ on other expenses .

He is left with Rs 9000

Let the salary of Rohit be x. Then

$x = \frac{x}{5}+\frac{x}{4}+\frac{x}{3}+\frac{x}{25}+9000%$, where

$\frac{x}{5}$ = Amount given to NGO
$\frac{x}{4}$ = Amount spent on food
$\frac{x}{3}$ = amount spent on rent
$\frac{x}{15}$ = amount spent on other expenses
9000 = balance.

The LCM of 5, 4, 3 and 15 is 60. Thus, we get

$x$= $\frac{12x+15x+20x+4x+540000}{ 60}$

$60x = 51x + 540000$

or $60x-51x = 540000$

$9x = 540000$

Therefore, $x = \frac{540000}{9} = 60,000$

Thus, Rohit's salary is Rs. 60,000.