Answer
$1302_{seven}$
Work Step by Step
Rightmost column: 5+4=9=1$\times$7+2=$12_{seven}$
record the 2, carry the 1.
. $( \ \ \ 1 \ \ )$
. ( 6 4 5 $)_{seven}$
+( 3 2 4 $)_{seven}$
$\_\_\_\_\_\_\_$
$ (\ \ \ \ \ \ \ \ 2 )_{seven}$
Next column:
$1+4+2=7=1\times7+0\times1=10_{seven}$
record 0, carry 1,
. $( \ 1 \ 1 \ \ )$
. ( 6 4 5 $)_{seven}$
+( 3 2 4 $)_{seven}$
$\_\_\_\_\_\_\_$
$ (\ \ \ \ \ 0 \ 2 )_{seven}$
Next column:
$1+6+3=10=1\times7+1\times1=13_{seven}$
record 13
. $( \ 1 \ 1 \ \ )$
. ( 6 4 5 $)_{seven}$
+( 3 2 4 $)_{seven}$
$\_\_\_\_\_\_\_$
$ ( 1 \ 3 \ 0 \ 2 )_{seven}$