The answer is D= undefined :)
First, let's convert the mixed fraction into an improper fraction (trust me, mixed fraction are pretty much the worst things to deal with, especially with higher level math):


Then, to subtract, since you need a common denominator, I would multiply the second fraction by 2 to get:

Now that we have a common denominator, we are ready to subtract:

Since that's the most simplified form, and you have been asked the question in a mixed fraction form, let's convert that to a mixed fraction. The remainder of the numerator divided by the denominator is 1, and the quotient is 3. The denominator stays the same. So, this is what results:

And that's your answer:

Hope this all makes sense. If anything doesn't, feel free to tell me!
Answer:
D
Step-by-step explanation:
Because the first equation is equivalent to 1, and d is equivalent to 1, the rest are incorrect
In its present form, there's not enough information to answer the question.
We'll need to know what you mean by the "radius" of an equilateral triangle,
or for that matter, the 'radius' of any triangle.