Mary gives away 26/2 = <<26/2=13>>13 blue shirts.
Mary gives away 36/3 = <<36/3=12>>12 brown shirts.
Mary has 26-13 = <<26-13=13>>13 blue shirts left.
Mary has 36-12 = <<36-12=24>>24 brown shirts left.
Mary has 13+24 = <<13+24=37>>37 shirts left.
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