Question

Exactly 120 tickets were sold for a concert. The tickets cost $12 each for adults, $10 each for seniors, and $6 each for children The number of adult tickets sold was equal to the number of child tickets sold. Given that the total revenue from the ticket sales was $1100, the number of senior tickets sold was
A:110
B:20
C:40
D:2
E:18

Answer 1

A=adult tickets
c=chlderenticekts
s=sinior tickets

a=c

a+c+s=120
2a+s=120

total made is 1100
12a+6c+10s=1100
sub
a=c
12a+6a+10s=1100
add
18a+10s=1100

multiply first equation by -9 and add to other equation

-18a-9s=-1080
18a+10s=1100 +
0a+s=20

s=20
20 senior tickets were sold

answer is B