1. Tim and Jonathan can paint a room in 2 h together. If Tim is painting the room alone, he can only complete the task in 6 h. How long will Jonathan take to paint a room all by himself?
2. Lu Lu Garments imported T-shirts from overseas and sorted them into 3 different colours. 3/7 of the T-shirts were red and 2/5 of the T-shirts were green. The rest of the T-shirts were yellow. There were 912 more green T-shirts than yellow T-shirts. How many green T-shirts were imported?
3. Mr Lee bought some T-shirts for $425. If he was given a discount of 15%, he would be able to buy 5 more identical T-shirts for the same amount of money. What was the original price of each T-shirt?
4. The price of one tuna bun from Sunshine Bakery is 70 cents. When a customer buys 5 tuna buns, he can buy one more at 30 cents. What is the greatest number of tuna buns that a customer can buy with $28?