Alison gave Anna 1/2 * 28 = 28/2 = <<1/2*28=14>>14 stamps.
Adding Alison’s stamps to Anna’s collection means Anna has 14 + 37 = <<14+37=51>>51 stamps.
Then Anna traded Jeff 2 stamps, so she had 51 - 2 = <<51-2=49>>49 stamps.
Anna got 1 stamp back in the trade, so she had 49 + 1 = <<49+1=50>>50 stamps in the end.
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