Why can't I use ratio in this ?? The Question:

Average salary of 60 employees is 12000 per month.
Number of executives is twice the no of non-executives.
If average salary of non-executives be 2/5th of the average salary of
executives then what is the average salary of non-executive employees
??

Answer is 6000.
I want to know why this is incorrect:

salaries in ratio =2:5
then  2x+5x=12000
x=12000/7

Please help me !!
And if anything is wrong let me know,
Thank you .
 A: Well, minimally,  your solution doesn't account for the fact that there are twice as many executives as there are workers.
Knowing that fact ($2W = E), and knowing that there are 60 employees, we know that
$$ W + E = 60 \\
W + 2W = 60 \\
3W = 60 \\
W = 20 $$
, where $W$ is the number of worker bees, so, there are $E = 2W = 40$ lazy tie-wearers.
Okay.  From the first fact, the average salary across 60 employees is \$12,000, so, the total money spent on salaries each month is $\$12{,}000 * 60 = \$720{,}000$.
As you did, we will let the basic salary unit be $x$.  Worker bees get 2 salary units ($2x$), and tie-wearers get 5 ($5x$).
Remembering that there are 40 execs and 20 workers, we can account for all the salary units:
$$ 20 \times 2x + 40 \times 5x = \$720{,}000 \\
40x + 200x = \$720{,}000 \\
240x = \$720{,}000 \\
x = $3{,}000 $$
So, \$3,000 is the basic salary unit.  Each worker makes 2 salary units, or \$6,000, and each exec pulls in \$15,000.  Each month.  \$180,000/yr.
Listen, that's just the way that I saw the problem.  If you saw it another way, and are now aware of your counting mistake, a piece of the puzzle that you didn't account for, great.  Work it out until it makes sense.
It's not that there's one right way to do it, or that you know the "best" way.  It's that you can find a way, and you can check that your answer is correct.
A: you have 20 non executives with an average salary $S$ and 40 executives with average salary $2.5 S$
thus
$$\frac{20\times S+40\times 2.5\times S}{60}=12,000$$
$$S=\frac{12,000\times 60}{120}=6,000$$
