2. The sum of two complex numbers greater than 10 is 3 1. Find these two numbers.
3. Use four numbers 2, 3, 5 and 7 to perform four operations. Each number can only be used once. What is the largest prime number that can be obtained?
4. What are the two natural numbers whose difference between a number divided by 9 and 2 and 4 and 6 is prime?
5. The product of three prime numbers is exactly equal to 1 1 times of their sum. Find these three prime numbers.
6. A van and an A&B leave relatively at the same time. When the van speed is 75km/ h and the car speed is 85km/ h, the two cars meet at a distance of 30km from the midpoint between the two places. Q: How many kilometers is it between A and B?