Question 1132437
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The way I read the given information, it is inconsistent, making it impossible to solve the problem.<br>
We need to determine the number of people who ordered each combination of the 3 items, enchiladas (E), chili con queso (C), and quesadillas (Q).  The possible combinations are {none, E, C, Q, EC, EQ, CQ, EQC}.<br>
(1) 21 ordered none: none = 21
(2) no one ordered only C: C = 0
(3) 5 ordered only Q: Q = 5
(4) 11 ordered all three: EQC = 11
(5) 29 ordered C or Q but not E: C+Q+CQ = 0+5+CQ = 29 --> CQ = 24
(6) 79 ordered either two or all three items: EC+EQ+CQ+EQC = 79 (we'll come back to this)
(7) 13 ordered E and Q but not C: EQ = 13
(8) 26 ordered only E and C: EC = 26<br>
Now going back to (6), we have EC+EQ+CQ+EQC = 79  -->  26+13+CQ+11 = 79  -->  CQ = 29<br>
But (5) says CQ is 24 and (8) says CQ is 29.