Answer:
So number of Adult tickets sold = A = 26.
Step-by-step explanation:
Define A, C, S as
A = number of adult tickets,
C = number of children tickets,
S = number of Senior tickets.
Then, by the statement of the problem, we have that
A = 8 + C,
S = 3C,
3C + 4S + 6A = 426,
so that
3C + 4(3C) + 6(8 + C) = 426
3C + 12C + 48 + 6C = 426
21C + 48 = 426
7C + 16 = 142
7C = 126
C = 126/7 = 18
A = 8 + 18 = 26
S = 3(18) = 54