EXPLANATION: Remember that a function is like a machine. F(x) is a machine and G(x) is also a machine. Plugging F into G is basically taking the output of the F machine and putting it into the G machine.
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if there are 10 girls and 6 boys total we have 16 students. Divide 10 by 16 which give 62% a girl will be picked and for boys divide 6 by 16 which is 38% a boy will be picked.