SOLUTION: There are 50 boys and 60 girls in the cafeteria .After x boys and x-5 girls left the cafeteria the probability of selecting a girl becomes 5/7,what is the value of x?

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Question 1040862: There are 50 boys and 60 girls in the cafeteria .After x boys and x-5 girls left the cafeteria the probability of selecting a girl becomes 5/7,what is the value of x?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
After x boys left, there are 50 - x boys remaining.
After x-5 girls left, there are 60 - (x-5) = 65 - x girls remaining.
==> %2865-x%29%2F%28%2850-x%29+%2B+%2865-x%29%29+=+5%2F7
<==> %2865-x%29%2F%28115-2x%29+=+5%2F7
==> 7(65-x) = 5(115-2x), after cross-multiplication.
==> 455 - 7x = 575 - 10x
==> 3x = 120 ==> highlight%28x+=+40%29.