Answer: 5 people
Explanation:
For this word problem, we can use the description in the problem to construct an equation. Let's use x for number of people.
3.5x+5.5x+6=51 [combine like terms]
9x+6=51 [subtract both sides by 6]
9x=45 [divide both sides by 9]
x=5
There were 5 people that went to the fair.