One member of the debate team is going to be chosen President. Each member is equally likely to be chosen. The probability that a boy is cho

(probability of a boy being chosen) + (probability of a girl being chosen) = 1.000

Let g be the probability of a girl being chosen.

Since the probability that a boy is chosen is 2/3rds the probability that a girl is chosen  --->   probability that a boy is chosen = (2/3)·g.

Substituting:       (2/3)·g + g  =  1.000

Adding the fractions:   (5/3)g  =  1.000

Solving for g:                     g  =  3/5                 (This means that girls make up 3/5ths of the club.)

I bet a lot of students get that one wrong.  The wording is really tricky.

Thanks Geno for that great answer.   :)