<PRE><B>Question 1129988</B>
this is an arithmetic sequence
:
x(n) = a +2(n-1)
:
a = 8
:
x(26) = 8 +2(26-1) = 58
:
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58 seats in row Z
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:
use the formula for the sum of the elements of an arithmetic sequence
:
sum = (n/2)*(2a +(n-1)d), where n=26, a=8, d=2
:
sum = (26/2)*(2*8 +(26-1)*2) = 858
:
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there are 858 seats in the auditorium 
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:
let a be the number of adult tickets, then number of student tickets is 2a
:
1) a +2a = 858
:
3a = 858
:
a = 286
:
286 adult tickets were sold and 572 student tickets were sold
:
let x be the cost of a student ticket, then 3x is the cost of an adult ticket
:
286*(3x) +572x = 2860
:
858x +572x = 2860
:
1430x = 2860
:
x = 2
:
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the student ticket costs $2
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