Hey there!!
How do we find the midpoint?
We take the average , the average is =
Sum of the observations / total number of observations
The end points are given as 4 and 11
Sum = 11 + 4
Number of observations = 2
= 15 / 2
= 7.5 is the midpoint
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Answer: Choice A</h3>
Why? Because the denominators are both the same at 2x+8. We can only add or subtract fractions when the denominators are the same. The general rule for adding fractions is

We have numerators A and B added together over a common denominator C. If we didn't have a common denominator, then we'd have to do a bit of algebraic manipulation to get both fractions to a common denominator. It doesn't have to be the lowest common denominator (LCD), though it's often more efficient that way.
C is your answer by the way