Solve for x. show the equation you used and your work.

Since the triangles in the figure are similar, then we have to
 ((14 + 6) / (14)) = ((21+ (x + 4)) / (21))
 Clearing for x
 ((20) / (14)) = ((25 + x) / (21))
 ((20) / (14)) * 21 = 25 + x
 x = ((20) / (14)) * 21-25
 x = 5
 answer
 x = 5

The first one is 2/3the second is 1/160the third is 4/125