5. (10 points) At the National Day garden party, there is a 100-person square formation. In the formation, each person's left hand either holds a red flower or a yellow flower. Each person's right hand either holds a red balloon or a green balloon. It is known that 42 people hold red flowers, 63 people hold red balloons, and 28 people hold yellow flowers in their left hand and green balloons in their right hand. Then, the number of people who hold red flowers in their left hand and red balloons in their right hand is.
【Answer】Solution: Green balloons: $100-63=37$ (people) hold red flowers and green balloons: $37-28=9$ (people) hold red flowers and red balloons: $42-9=33$ (people) Answer: There are 33 people who hold red flowers in their left hand and red balloons in their right hand. Therefore, the answer is: 33.