Respuesta :

pegah
at first, you should say:
6 7/10 = 67/10 and 3 4/5 = 19/5 
now you can say:
19/5 = 38/10 
so the answer is: 
67/10 - 38/10 = 29/10 or 2.9 :)))
i hope this ia helpful 
have a nice day