GMAT Data Sufficiency (DS) | Re: How many of the 42 people in a group are employed students

Here's a step-by-step approach using theDouble Matrix method .

Here, the criteria are:
- employment status (employed or unemployed)
- schooling (student or non-student)

There are 42 people altogether, so our first diagram looks like this:

Notice that I placed a star in the top-left box.
...

---