To find the median of the set of numbers {20, 30, 40, 50, 60, 70, 80}, we first arrange the numbers in order (which they already are) and then find the middle value.
Since there are 7 numbers in the set (an odd number), the median is the value at the position given by the formula:
\[ \text{Median position} = \frac{n + 1}{2} \]
where \( n \) is the number of values in the set. Here, \( n = 7 \):
\[ \text{Median position} = \frac{7 + 1}{2} = \frac{8}{2} = 4 \]
The 4th number in the ordered set is 50.
Thus, the median of the set {20, 30, 40, 50, 60, 70, 80} is 50.
Looking at the provided options, C 5050 could be interpreted as a formatting issue, but the actual median value is 50. If it were based on the value alone, the correct choice based on the accurate median would be:
C.