Ateacher buys 50 train tickets for a school trip for a total cost of $1,200. she buys x number of student tickets for $20 each. she also buys y number of adult tickets for $30 each. how many adult tickets did she buy?

y=20 , x =30

Step-by-step explanation:

x+y=50;  

20x+30y=1200

20x+20y=1000, multiplying the top by 20

-20x-30y=-1200, subtracting the second.

-10y=-200

y=20 adult tickets ($600)

x=30 student tickets ($600)

(add up to $1200)

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