Answer
$1526_{seven}$
Work Step by Step
Rightmost column: $2$+4=$6$=$6\times 1$=$6_{seven}$
record the $6$, no carry.
$\left[\begin{array}{llll}
& & & \\
& 6 & 3 & 2_{seven}\\
+ & 5 & 6 & 4_{seven}\\
- & - & - & -\\
& & & 6_{seven}
\end{array}\right.$
Next column:
$3+6=9=1\times7+2\times1=12_{seven}$
record the 2, carry the 1.
$\left[\begin{array}{llll}
& 1 & & \\
& 6 & 3 & 2_{seven}\\
+ & 5 & 6 & 4_{seven}\\
- & - & - & -\\
& & 2 & 6_{seven}
\end{array}\right.$
Next column:
$1+6+5=12=1\times7+5\times1=12_{seven}$
record the $15$,
$\left[\begin{array}{llll}
& 1 & & \\
& 6 & 3 & 2_{seven}\\
+ & 5 & 6 & 4_{seven}\\
- & - & - & -\\
1 & 5 & 2 & 6_{seven}
\end{array}\right.$
