Question 1173796
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The number of jewels, originally, is  4 + 7 + 5 = 16.


The probability is  P = {{{(5/16)*(4/15)}}} = {{{(5/4)*(1/15)}}} = {{{1/(4*3)}}} = {{{1/12}}}.    <U>ANSWER</U>
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Solved.


The formulas are SELF-EXPLANATORY.