Question: Ivan had $10 and spent 1/5 of it on cupcakes. He then spent some money on a milkshake and had only $3 left. How much is the milkshake?
Answer: Ivan spent a total of $10 - $3 = $7 on cupcakes and a milkshake. The cost of the cupcake is $10 x 1 / 5 = $2. So, $7 - $2 = $5 was spent on the milkshake. The answer is 5.

Question: Reese joined a Pinterest group where members contributed an average of 10 pins per day. The group owner deleted older pins at the rate of 5 pins per week per person. If the group has 20 people and the total number of pins is 1000, how many pins would be there after Reese had been a member for a month?
Answer: In a day, the total number of new pins is 10 * 20 = 200. There will be 30 * 200 = 6000 new pins after a month. The total number with old pins present is 6000 + 1000 = 7000 pins. If the owner deletes five pins every week, the total number of deleted pins in a week is 5 * 20 = 100 pins. After a month, the number of deleted pins will be 100 * 4 = 400. The number of pins after the old pins are deleted is 7000 - 400 = 6600 pins. The answer is 6600.

Question: Rose bought a plant with a 10% discount. If the price is $10, how much did Rose pay after the discount?
Answer: The plant has $10 x 10 / 100 = $1 discount. So, Rose paid $10 - $1 = $9 for the plant. The answer is 9.

Question: Will and Henry go fishing in a river. Will catches 16 catfish and 10 eels. Henry challenges himself to catch 3 trout for every catfish Will catches. Due to environmental concerns, Henry decides to return half his catch after meeting his own challenge. How many fishes do they have altogether now?
Answer:
Will caught 16 + 10 = 26 fishes. Henry caught 3 trout for each catfish Will caught so since Will caught 16 catfish, Henry caught 16 * 3 = 48 trout. Half of 48 trout is (1 / 2) * 48 = 24. Henry returned 24 trout leaving him with 48 - 24 = 24 trout. They now have a total of 26 + 24 = 50 fishes. The answer is 50.