Answer:
A. 3
Explanation:
ΔDEC is bigger than ΔABC by 5. For the hypotenuse, 25 is 5 times bigger than 5.
So, side DE on ΔDEC has to be 5 times bigger than side AB on ΔABC.
If side AB equals 3, side DE equals 18 - 3, which is 15.
15 is five times bigger than 3, so the answer is A. 3.
Hope that helps.