9514 1404 393
Answer:
 73
Step-by-step explanation:
Let m, g, o represent the numbers sold by Mookie, Gandalf, and O'Malley, respectively. Then the relations between these values are ...
 g = 3m -5
 o = 7m +1
 o = 4 +2(m +g)
Equating expressions for o, we have ...
 7m +1 = 4 +2(m +g)
Substituting for g, we have ...
 7m +1 = 4 +2(m +(3m -5))
 7m +1 = 8m -6
 7 = m . . . . . . . . add 6-7m
 g = 3·7 -5 = 16
 o = 7·7 +1 = 50
The number sold in total is ...
 m + g + o = 7 +16 +50 = 73
They sold 73 tickets in total.