Answer
Junction rule
$I_1 - I_2 +I_3 =0$
loop rule
loop ABCD
$I_1R_1 -7.0V - I_3R_3-3.0 V =0$
Loop BEFC
$ I_2R_2 - 5.0 V + I_3R_3 +7.0V =0$
Work Step by Step
Junction rule will apply at B
$I_1 - I_2 +I_3 =0$
by Kirchhoff loop rule
in loop ABCD
$I_1R_1 -7.0V - I_3R_3-3.0 V =0$
in Loop BEFC
$ I_2R_2 - 5.0 V + I_3R_3 +7.0V =0$
