Norma left 9 T-shirts And twice as many sweaters, she took 9 * 2= <<9*2=18>>18 sweaters
Adding the T-shirts and sweaters, Norma left 9 + 18 = <<9+18=27>>27 clothes
When she came back, she found 3 sweaters And triple the number of T-shirts, she found 3 * 3 = <<3*3=9>>9 T-shirts
Adding the T-shirts and sweaters, Norma found 3 + 9 = <<3+9=12>>12 clothes
Subtracting the clothes she left from the clothes she found, 27 - 12 = <<27-12=15>>15 clothes are missing
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