Mathematical thinking training in kindergarten teacher class: 1. The mall sent back 28 TV sets and sold some of them, leaving 15. How many TV sets have been sold? 2. Xiaohu learned to write brush strokes. I wrote six on the first day, and then I wrote three more every day than the day before. How much did he write in four days? Xiaoyun is 8 years old this year. Grandma said, "I will be 62 years old when you are 12 years old." How old is grandma this year? 4. What is the result of subtracting the minimum two digits from the minimum three digits and then subtracting the minimum one digit? It takes five minutes for five children to eat five apples at once. At this rate, how many minutes will it take for 10 children to eat 10 apples at the same time? 6. Xiaohua has 10 red balloons, and Xiaohua has 8 yellow balloons. Xiaohua exchanged four red balloons for three yellow balloons for Xiaohua. How many balloons does Kobanawa Xiaohua have now?