Answer: option (d)
Explanation:
Our task is to find out which of these fractions is not equivalent (equal) to 1/3.
To determine that, I am going to simplify each of these fractions:

Divide the top & bottom by 5:


So, option A is out!
---------------------------------------- Option B ---------------------------------------------------

Divide the top & bottom by 6:


Two down, two to go! This one's also out.
---------------------------------------- Option C ---------------------------------------------------

Divide the top & bottom by 4:


Let's take a look at option d.
---------------------------------------- Option D ---------------------------------------------------

Unlike all of the fractions above, 7 and 20 have no common factors (except 1, and there's no point in dividing by 1!), so, this is the one that isn't equivalent to 1/3.
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