I like to draw a diagram for these questions. (see below)

For three sets there are 8 regions including the outside. But for your problem you can assume that the three 'only one subject' regions and the outside are all zero.

So call the one you have to find x.

Make up algebraic expressions for the other regions and add them up.

Make an equation by setting this equal to 500.

Solve for x.

Bob

]]>I am looking at two solutions to this problem and both of them are algebraic.

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I am like really really confused on how to solve this I uploaded a picture of what I did then am just stuck and confused.

15. 500 students are enrolled in at least two of these three classes: Math, English, and History. 170 are enrolled in both Math and English, 150 are enrolled in both History and English, and 300 are enrolled in Math and History. How many of the 500 students are enrolled in all three?

A 300

B 330

C 200

D 120

E 90

F 60