48% of respondents to a survey consisted of those who used both M and N and those who used neither M nor N. 46% of respondents did not use M. 42% used N. What percent of respondents used only N?	Choose the correct choice from the following choices:
A) 19.5%	B) 21.5%	C) 20%	D) 18.5%	E) 17.5%
From the question, we can summarize the information as follows:   N Not N   M X   Not M Ans y 46   42 100   Then we can set a system of 3 equations 3 unknowns described below:   X + Y = 48   X + Ans = 42   Y + Ans = 46   Sum up all three equations to get 2X + 2Y + 2Ans = 136   Divide both sides by 2 to get X + Y + Ans = 68   Replace X + Y with 48 to get 48 + Ans = 68   Substract 48 from both sides to get Ans = 68 - 48= 
<gadget id="calculator">68 - 48</gadget>
<output>20</output>
20   The answer must be 20%.
<result>C</result>
48% of respondents to a survey consisted of those who used both M and N and those who used neither M nor N. 46% of respondents did not use M. 42% used N. What percent of respondents used only N?