Question 662016
x = adult
y = children's
7x+5y=104
any multiple of 5 will end with 0 or 5
subtract multiples of 7 from 104 until getting an integer ending in 0 or 5
x could be 2 or 7 or 12
7(2) + 5y = 104
14 + 5y = 104
5y = 90
y = 18
2 adults, 18 children's
OR
7(7) + 5y = 104
49 + 5y = 104
5y = 55
y = 11
7 adults, 11 children's
OR
7(12)+ 5y = 104
84 + 5y = 104
5y = 20
y = 4
12 adults, 4 children's