Mental Math Shortcuts

need help solving this problem!

Consider the fallowing data taken from a certain theater in a local theater. Ages 1-50 and 51-100
Badman and Spiderman, movie.

ages 1-50 13 people saw Badman
ages 50-100 7 people saw Badman
ages 1-50 12 people saw Spiderman
ages 50-100 18 people saw Spiderman

a) If one person is selected, find the probability they were in 1-50 group or saw Spiderman

b) If one person is selected, find the probability they were in 50-100 group saw Badman

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