50% of the vote is 100 votes because 200 x .5 = <<200*.5=100>>100
Just over 50% is 101 votes because 100 + 1 = 101
120 students are boys because 200 x .6 = <<200*.6=120>>120
80 students are girls because 200 - 120 = <<200-120=80>>80
She gets 81 votes from boys because 120 x .675 = <<120*.675=81>>81
She needs 20 votes from girls because 101 - 81 = <<101-81=20>>20
She needs a proportion of .25 of girl's votes to win because 20 / 80 = <<20/80=.25>>.25
The percentage she needs is 25 because 100 x .25 = <<100*.25=25>>25
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