Gabrielle thinks of a number.
She then does the following operations:
Multiply by 2, subtract 4, multiply by 3 then add 20 (in that order).
She finds that the number she ends up with is 8 times her original number.
What was Gabrielle's original number?
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This question is best answered by forming an algebraic equation then solving it. Let Gabrielle's original number be x.
First operation gives 2x
Second operation gives 2x 4
Third operation gives 3(2x 4)
Fourth operation gives 3(2x 4) + 20
This is equal to 8 times the original number
3(2x  4) + 20 = 8x
6x 12 + 20 = 8x
...
x = 4
Gabrielle's original number was 4.
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