Hi,

let there be x tickets sold at $10,

so, the tickets sold at $70 would be (30-x).

and total revenue would be: $10(x)+$70(30-x)

Using (1)

1570 < 10(x)+70(30-x) < 1670

or 1570 < 10x + 2100 - 70x < 1670

or 1570-2100 < -60x < 1670-2100

or -530 < -60x < -430 (multiply by -1)

or 430 < 60x < 530

or 7.16 < x < 8.33,

since x is integer and only one value exist between 7.1 & 8.3, i.e., 8

thus, x=8. Sufficient.

Using (2),

20 < special exhibit ticket < 25

or 20 < 30-x < 25

or -10 < -x < 5

or 5 < x <10,

thus, x = 6, 7, 8, 9

Clearly, not sufficient.

Thus, Answer is (A).

Regards,

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