Let X be the no. of voters who responded favorable for both candidates, M and N.sud21 wrote:
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(1) The number of voters who did not respond favorable for either candidate was 40 implies that the voters responded favorable for at least one 100 - 40 = 60 = 70-x or x = 10; SUFFICIENT.
(2) The number of voters who responded unfavorable for both candidates was 10 is clearly NOT sufficient.
The correct answer is A.
