Final answer:
To determine Mr. Jonson's age, we can use the information that his age is a multiple of 9 this year and will be a multiple of 4 next year. By listing the possible ages that are multiples of 9 and finding which ones are also multiples of 4, we can determine that Mr. Jonson's age is 36.
Step-by-step explanation:
To determine Mr. Jonson's age, we can use the information that his age is a multiple of 9 this year and will be a multiple of 4 next year. Since his age is a multiple of 9 this year, we can list the possible ages that are multiples of 9: 9, 18, 27, 36, 45, ... Next, we need to find an age that is a multiple of 4 next year. Therefore, we can find which ages from our list are also multiples of 4. The only age that satisfies both conditions is 36. So, Mr. Jonson's age is 36.