At Billy's school, 80 students bone to school by bike or car. Together the vehicles arrive to school in have 270 wheels. How many of each are used? Use "b" to represent the number of bicycles and "c" to represent the number of cars

25 bikes and 55 cars were used.

Step-by-step explanation:

Let b represent number of bicycles that the students ride to school.

Let c represent number of cars that the students drive to school.

At Billy's school, 80 students come to school by bike or car. It means that

b + c = 80

A bike has 2 wheels. A car has 4 wheels. Together the vehicles that arrive at the school have 270 wheels. It means that

2b + 4c = 270- - - - - - - - - - 1

Substituting b = 80 - c into equation 1, it becomes

2(80 - c) + 4c = 270

160 - 2c + 4c = 270

- 2c + 4c = 270 - 160

2c = 110

c = 110/2

c = 55

b = 80 - c = 80 - 55

b = 25

144 p

Step-by-step explanation:

It was due to be returned on 26 November but she returned it on 12 December.

She was therefore with it for an extra 16 days.

The fine is 9p per day. Therefore, she will pay a fine of:

9 * 16 = 144 p