Answer
$1000_{two}$
Work Step by Step
Rightmost column:
$1+1=2=1\times 2+0\times 1=_{}10_{two}$
record the $0 $( carry the 1):
$.\qquad \quad\ $1
$.\qquad \ $1 0 $1_{two}$
$.\quad +\ \ \ \ \ $1 $1_{two}$
$.\quad \quad \_\_\_\_$
$.\qquad \quad \ \ 0_{two}$
Next column:
$1+0+1=2=1\times 2+0\times 1=_{}10_{two}$
record the $0 $( carry the 1):
$.\qquad\ 1\ $1
$.\qquad\ $1 0 $1_{two}$
$.\quad +\ \ \ \ \ $1 $1_{two}$
$.\quad \quad \_\_\_\_$
$.\qquad\quad 0 \ 0_{two}$
Next column:
$1+1=2=1\times 2+0\times 1=_{}10_{two}$
record the $10 $
$.\qquad\ 1\ $1
$.\qquad\ $1 0 $1_{two}$
$.\quad +\ \ \ \ \ $1 $1_{two}$
$.\quad \quad \_\_\_\_$
$.\quad\ 1\ 0\ 0 \ 0_{two}$
Check in base 10:
5+3=8
