4_<8> + 7_<8> =

(a)  

10_<8> + 2_<8> =

(a)  

14_<8> + 4_<8> =

(a)  

7_<8> - 2_<8> =

(a)  

15_<8> - 6_<8> =

(a)  

42_<8> - 31_<8> =

(a)  

51_<8> - 37_<8> =

(a)