Final answer:
Dan sent 15 messages, Henry sent 60 messages, and Susan sent 22 messages.
Step-by-step explanation:
To solve this problem, we can set up a system of equations. Let's assign variables to each person's number of messages. Let's say Dan sent x messages. Then Henry sent 4x messages, and Susan sent x + 7 messages. The total number of messages sent is the sum of these three variables, which is x + 4x + (x + 7) = 97. Simplifying this equation, we get 6x + 7 = 97. Subtracting 7 from both sides, we have 6x = 90. Finally, dividing both sides by 6, we find that x = 15. So Dan sent 15 messages, Henry sent 4 times that, which is 60 messages, and Susan sent 15 + 7, which is 22 messages.