Respuesta :

9 and three are the missing digits
The first box is 9 because the second box is 3...

 since 3 is smaller than the 6 then you have to take one from the nine then it would make 8... so the one would take place in front of the 3 and make it a 13... 
4-8=4
13-6=7

I hope this helps!!! <33