What is the length of cd in this diagram abc ~ edc

C. 5

Step-by-step explanation:

Given the two triangles are similar, then its sides are proportional. In consequence the following relation must be satisfied:

BC/AC =  CD/CE

Replacing with the given values and solving for x, we get

(20 - x)/21 = x/7

(20 - x) = 21*x/7

20 - x = 3*x

20 = 3*x + x

20 = 4*x

20/4 = x

5 = x

a complex number is a number that can be expressed in the form a + bi, where a and b are real numbers, and i is a solution of the equation x2 = −1. because no real number satisfies this equation, i is called an imaginary number. has no real solution, since the square of a real number cannot be negative.