[Question]: A shop sells laptops at $600 each and a smartphone at $400. Celine buys two laptops and four smartphones for her children. How much change does she get back if she has $3000?
[Answer]: The cost of the two laptops is 2 x $600 = $1200. The cost of the four smartphones is 4 x $400 = $1600. Thus, the total cost of all the items is $1200 + $1600 = $2800. Therefore, Celine gets a change of $3000 - $2800 = $200.
So the answer is 200.

[Question]: Tim had a birthday party with a clown that cost $100 an hour for 4 hours. He also rented a bounce house for half the time that cost 3 times as much an hour. Everything else for the party cost $1000. How much did his birthday cost?
[Answer]: The clown cost 100 * 4 = $400. The bounce house cost 100 * 3 = $300 per hour. He rented it for 4 / 2 = 2 hours. So it cost 300 * 2 = $600. That means the total cost was 400 + 600 + 1000 = $2000.
So the answer is 2000.

[Question]: Veronica, who is the team captain of their school football team, carried 27 yellow balls and 33 brown balls to the field for the team's matchday practice. What percentage of the balls that she carried were yellow?
[Answer]:
The total number of balls that she carried is 27 + 33 = 60. The percentage that represents the yellow balls is 27 / 60 * 100% = 45%.
So the answer is 45.