Respuesta :

Answer:

C-(7)

Step-by-step explanation:

Given figure is a trapezoid and 21 - x is the mid segment.

Therefore by mid-segment formula of a trapezoid, we have:

21 - x = 1/2(17 + 11)

21 - x = 1/2 * 28

21 - x = 14

21 - 14 = x

7 = x

x = 7