Q: Martha has 18 crayons. She lost half of them, so she bought a new set of 20 crayons. How many crayons in total does Martha have after the purchase?
A: In the beginning, Martha lost 18 / 2 = 9 crayons. So after she bought a set of new crayons, she has in total 9 + 20 = 29 crayons. The answer is 29.

Q: Mike buys 6 rose bushes at 75 dollars each, 2 of them are for his friend and the rest are for him. He also buys 2 tiger tooth aloes for 100 dollars each. How much money did he spend on plants for himself?
A: He bought 6 - 2 = 4 rose bushes for himself. The rose bushes for himself cost 4 * $75 = $300. He also spent 2 * $100 = $200 on aloes. He spent a total of $200 + $300 = $500. The answer is 500.

Q: Kris is blowing u balloons for her sister's party. She has 30 minutes to blow up as many balloons as possible and decides to enlist her brother's help to increase the number of balloons. Kris can blow up a total of 2 balloon per minute, and her brother works twice as fast. After 15 minutes, her brother doubles his speed and works at this new speed for the remaining 15 minutes. After the 30 minutes, how many balloons, in total, did Kris and her brother blow up?
A:
Throughout the 30 minutes, Kris blows up 2 balloons per minute * 30 minutes = 60 balloons. Her brother works at double Kris' speed in the first 15 minutes so he works at 2 balloons per minute * 2 = 4 balloons per minute. So in the first 15 minutes, he blows up 4 balloons per minute * 15 minutes = 60 balloons. In the second 15 minutes, he is working at double the rate he did previously, so he blows up 4 balloons per minute * 2 = 8 balloons per minute. In the second 15 minutes, Kris' brother therefore blows up 8 balloons per minute * 15 minutes = 120 balloons. Throughout the 30 minutes, he has blown up a total of 60 + 120 = 180 balloons. Kris and her brother therefore blew up a total of 60 balloons from Kris + 180 balloons from Kris' brother = 240 balloons. The answer is 240.