math
posted by bell .
Adult tickets for a play cost $19 and child tickets cost $17. If there were 36 people at a performance and the theatre collected $646 from ticket sales, how many children attended the play?

Let a = adults and c = children.
a + c = 36 total attendance, then
a = 36  c
19a + 17c = $646 total ticket sales
Substitute (36c) for a in the second equation and solve for c.
I'll let you do the calculations. 
C=19

Which expression shows the cost of one adult
admission ticket and 9 thrill ride tickets?
A $15 + (9 × $3)
B $12 + (9 × $3)
C $15 + (9 + $3)
D ($15 × 9) + $3 
b

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