66% of respondents to a survey consisted of those who used both M and N and those who used neither M nor N. 53% of respondents did not use M. 47% used N. What percent of respondents used only N? Options.
A) 19.5%  B) 21.5%  C) 20%  D) 18.5%  E) 17%
From the question, we can summarize the information as follows:   N Not N   M X   Not M Ans y 53   47 100   Then we can set a system of 3 equations 3 unknowns described below:   X + Y = 66   X + Ans = 47   Y + Ans = 53   Sum up all three equations to get 2X + 2Y + 2Ans = 166   Divide both sides by 2 to get X + Y + Ans = 83   Replace X + Y with 66 to get 66 + Ans = 83   Substract 66 from both sides to get Ans = 83 - 66= 
<gadget id="calculator">83 - 66</gadget>
<output>17</output>
17   The answer must be 17%.
<result>E</result>
66% of respondents to a survey consisted of those who used both M and N and those who used neither M nor N. 53% of respondents did not use M. 47% used N. What percent of respondents used only N?