Question 1042934
First let's simplify the expression for x. 



{{{x=1+(1/2)+(1/4)+(1/8)}}}



{{{x=8/8+4/8+2/8+1/8}}}



{{{x=(8+4+2+1)/8}}}



{{{x=15/8}}}



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Now plug {{{x=15/8}}} into the equation for 'a'



{{{a=1+(1/2)*x}}}



{{{a=1+(1/2)*(15/8)}}} Replace x with 15/8



{{{a=1+(1*15)/(2*8)}}}



{{{a=1+15/16}}}



{{{a=16/16+15/16}}}



{{{a=(16+15)/16}}}



{{{a=31/16}}}



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We now know the values of "a" and "x". Let's subtract them. 



{{{a-x = 31/16-15/8}}}



{{{a-x = 31/16-30/16}}}



{{{a-x = (31-30)/16}}}



{{{a-x = 1/16}}}



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The final answer is choice B) 1/16