There are an infinite number of different equations that have
x=2/3 as the solution, or as one of several solutions.
You didn't show us your list of choices, so we can't help you
pick the right one.
Just take each choice, one at a time. Write ' 2/3 ' in place of 'x'
in each equation, and simplify everything. You'll wind up with
one equation that's true, and the others will say something that's
nonsense.
The one that's true is the one that has x=2/3 as its solution.
We have

of 252 people who have a personalized black disc
Number of people who would have personalized flying disc =

people
Then we work out the number of people who like to play disc golf:

people
So we have 15 people who like to play disc golf and have personalised black disc.
#7 is C-180°
it’s a fact all angles of a triangle add up to 180°