Look at the given figure. If the triangles are congruent, give the theorem. If not, select not congruent. No links please

Acronym to remember the 3 basic trigonomic functions: 

Soh - Cah - Toa 

             opposite
sin =
            hypotenuse

              adjacent 
cos =
             hypotenuse

             opposite 
tan =  
             adjacent 

In your case, you can set up a sine trigonomic function, like this: 

Sin 48 = 10      (adjacent)
                 
                 x       (hypotenuse)

                       10
 (x) Sin 48 = (x)
                         x

  (x) Sin 48 = 10 
     
  Sin 48         Sin 48 

Plug in 10(sin)(48) into a calculator.

x = 7.43

I just realized that you didn't ask me to find the answer, but now you will know even more than you need to :D