Answer:
D) 5
Explanation:
Since the two triangles are similar:
therefore:
AC/CE = BC/CD
We are given that:
AC = 21
CE = 7
BC = 20-x
CD = x
Substitute with the givens in the above relation and solve for x as follows:
AC/CE = BC/CD
21/7 = (20-x) / x
3 = (20-x)/x
3x = 20-x
3x+x = 20
4x = 20
x = 20/4
x = 5
Now we have:
BC = 20-x = 20-5 = 15
CD = x = 5
Hope this helps :)
