Isabella and Alexis went to the mall to buy some pants and dresses. Alexis bought 3 times more pants and dresses than Isabella. If Alexis bought 21 pairs of pants and 18 dresses, how many pairs of pants and dresses did Isabella buy in total?
The number of pants Isabella bought is 21 / 3 = <<21/3=7>>7 pairs of pants.
The number of dresses Isabella bought is 18 / 3 = <<18/3=6>>6 dresses.
The total number of pants and dresses Isabella bought is 7 + 6 = <<7+6=13>>13.
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