Question 1082510
  Since triangle ABC & triangle DFE are congruent, their corresponding sides    should also be congruent. So,

m(AB) = m(DE) = 10. So,

m(DE) = 10 = {{{1/2}}}x+2. So,
 
        10-2 = {{{1/2}}}x+2-2

        8 = {{{1/2}}}x

        x = 8*2

        x = 16 units.  Answer. If you have any doubt, feel free to mail gsmani9@yahoo.com.
        God bless you.