Question

The cost of hiring a van is partly constant and the other varies with the time spent. It costs 180 for a 2 hours hire and 450 for a 7 hours

Answer 1

c = mt+b
you are given
2m+b = 180
7m+b = 450

Now do what you want with that -- you did not ask a question

Answer 2

C = cost

t = time

C = a + b • t

where

a and b are constants

Substitute the given values in the equation:

a + b • t = C

t = 2 h , C = 180

a + b • t = 180

a + b • 2 = 180

a + 2 b = 180

t = 7 h , C = 450

a + b • t = 450

a + b • 7 = 450

a + 7 b = 450

Now solve system of two equations:

a + 2 b = 180

a + 7 b = 450

The solution is:

a = 72 , b = 54

The cost is:

C = a + b • t

C = 72 + 54 t