So I've never stumbled upon this type of problem (Vienn diagram) until I noticed it in Rhyme's gmat-knowledge pdf.
So I want to know if I did it correcly, since it doesn't provide the final answer.
20 people are on marketing team, 30 on sales,
40 on vision. 5 are on both marketing and sales, 6 on sales
and vision, 9 on both marketing and vision, 4 in all three.
How many workers are there in total?
PROBLEM II from MGMAT:
In a group of 68 students, each student is registered for at least one of three classes â€“ History, Math and English. Twenty-five students are registered for History, twenty-five students are registered for Math, and thirty-four students are registered for English. If only three students are registered for all three classes, how many students are registered for exactly two classes?