9514 1404 393
Answer:
x = 6
Step-by-step explanation:
The parallel lines divide the side lengths proportionally.
21/14 = (x+3)/x
1.5 = 1 +3/x . . . . perform the division
0.5 = 3/x . . . . . .subtract 1
x = 6 . . . . . . . . . multiply by 2x
