Answer :
Total people who shopped = 409
Total people who shopped at Trader Joes = 104
Probability someone shopped at trader Joes: 104/409 = 0.254 x 100 = 25.4%
Total who live on Northside and shop Trader Joes = 70
Probability = 70/409 = 0.171 x 100 = 17.1%