Let x be the reservation charge and h be the cost of half ticket.
From condition 2:
cost of total full ticket = cost of full ticket + cost of reservation
400 = cost of full ticket + x
hence,
cost of full ticket = 400 – x
From condition 1:
cost of half ticket = ¾ * cost of full ticket
= ¾ *(400 - x)
cost of total half ticket : ¾ *(400 - x) + x
From condition 3:
Cost of total full ticket + 2*cost of total half ticket = 1050
400 + 2* (¾ *(400 - x) + x) = 1050
2* (¾ *(400 - x) + x) = 650
¾ *(400 - x) + x = 325
1200 -3x + 4x = 1300
x = 100