Plz look at the attach photo . to help thank you

Answer:
your answer is correct.. its 10
Step-by-step explanation:
as you can see the line DC and EF are the same exact length.
CM =5
line CM is half of line DC. which means to fine the length of EF you must multiply 5 by 2 (5×2) to get the length of EF which is 10
hope this helps