The cost of hiring a van is partly constant and partly varies with the time spent it cost 180 for 2 hours hire and 450 for a 7 hours a write an equation connecting the cost x with the time t.b,find the cost for 10 hours
x = at + b
when x = 180, t = 2 ----> 2a + b = 180
when x = 450, t = 7 ----> 7a + b + 450
subtract them:
5a = 270
a = 54
and then 108 + b = 180
b = 72
equation : x = 54t + 72
sub in t = 10 to find x