Math Problem Solver

$$168 + 123=291$$

$$\begin{aligned} \mathtt{1}\overset{\mathtt{1}}{\mathtt{6}}\mathtt{8}\\ \mathtt{+\phantom{0}}\mathtt{1}\mathtt{2}\mathtt{3}\\ \hline \mathtt{2}\mathtt{9}\mathtt{1} \end{aligned}$$

$1$ is the digit in the $10^{0}$ place. $8 \times 10^{0} + 3 \times 10^{0} = 11 \times 10^{0} = 1 \times 10^{1} + 1 \times 10^{0}$.$1 \times 10^{1}$ carries to the $10^{1}$ place.

$9$ is the digit in the $10^{1}$ place. $1 \times 10^{1} + 6 \times 10^{1} + 2 \times 10^{1} = 9 \times 10^{1}$.

$2$ is the digit in the $10^{2}$ place. $1 \times 10^{2} + 1 \times 10^{2} = 2 \times 10^{2}$.