Chapter 3.2B, Problem 16A

Hector computed his addition problems by placing the partial sums as shown here:

$\begin{array}{l}\underset{\_}{\begin{array}{l}768\\ +647\end{array}}\\ 15\\ 10\\ \underset{\_}{13}\\ 1415\end{array}$

Use this method to work the following addition problems.

a. $\underset{\_}{\begin{array}{l}987\\ +356\end{array}}$

b. $\underset{\_}{\begin{array}{l}415\\ +79\end{array}}$