As with all word problems, it's imperative that you diagram everything correctly, and not get confused with what the statement says.
First, write down what you know:
Total # of employees (T) = 800
- # of long term employees (L) = 0.7 * 800 = 560
- # of long term employees retiring (y) = y
Next, identify what the question is asking. Basically, you're solving for y, such that when you take the ratio of long term employees (L) over total employees (T), it equals 60% , or 0.6.
So, your next task is to write this in equation form. You know that the ratio of L / T can be written as
560 / 800
However, this doesn't take into account the people who are retiring (y). Next step is to take into account these retiring people. You know that you started with 560 Long term employees, and y are leaving. So L now becomes 560-y. Similarly, you originally had 800 Total employees, but y left, so you would rewrite T as 800-y. So, your equation now becomes
(560-y) / (800-y) = 0.6
It equals 0.6 because the problem tells you that the ratio has to be 60%, or 0.6. Now all that's left is to solve the equation for y
560-y = 480 - 0.6y
80 = 0.4y
y = 200
which is the credited response.
Don't let the fact that the company is named 'x' (and is in bold) fool you. Take the time to read the statement carefully and write down everything you know first. From there, identify what is being asked, and only then start to translate everything into your final equation.
my GMAT debrief:
https://www.beatthegmat.com/came-through ... 44327.html
You will not fear the terror of night, nor the arrow that flies by day,
nor the pestilence that stalks in the darkness, nor the plague that destroys at midday.
A thousand may fall at your side, ten thousand at your right, but it will not come near you.
- Psalm 91: 5-7
