To determine the minimum cost of he transportation given the constraints and the costs of the transportation mode, we need to set up equations. We do as follows:
Let C be the total cost so that the total cost would have an expression:
C = 1200x + 100y where x is the number of buses and y is the number of vans to be rented.
We are given the total number of students, this would be equal to:
400 = 40x + 8y
Also, for the 36 teachers:
36 = 3x + y
We have three unknowns and three equation so we can solve the values of the unknowns. We do as follows:
36 = 3x + y
y = 36 - 3x
400 = 40x + 8y
400 = 40x + 8(36 - 3x)
x = 7
y = 36 - 3(7)
y = 15
C = 1200x + 100y
C = 1200(7) + 100(15)
C = 9900 <------- minimum total cost