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I Need To Review Venn Diagrams - Math Discussion

I need to review venn diagrams

Hello,
I'm preparing for an exam an came across this question from 800score. Please help me understand this problem.
If, in a certain school, 20 students play soccer, 10 play basketball, and 7 play both, how many students play basketball, soccer or both?
Please review this question and help me solve it as my exams are nearing.