We can write this situation as follows, and from it we can derivate possible options:
She bought one soft drink ($3) and 6 candy bars, and spent a total of $33:
3 + 6x = 33 [1]
This equation translates the situation (mathematically).
Then, we can say, that (solving for x):
Subtracting 3 to both sides of equation [1]:
3 - 3 + 6x = 33 - 3
0 + 6x = 30
Dividing both sides by 6, we finally have that the cost of each candy bar is:
6x/ 6 = 30/6
x = 5.
We can check this:
6 candy bars * $5 = $30
$30 + $3 = $33.
We can see from options that (using equation [1]) option D is one of the possible answers:
6x + 3 = 33 = 3 + 6x = 33
Evaluation of the other options:
1. Option A is not the same as [1]
x/6 + 3 = 33 is different to 3 + 6x = 33.
2. Option B is not the same as [1]
3x + 6 = 33 is different to 3 + 6x = 33.
Option C x = 33/3 + 6 is different to [1]. In [1] x = (33 - 3)/6
So, option D, is the possible answer.