Calculate the following.

Example:

\[
3432 \times 26
\]

\[
\begin{array}{r}
3432 \\
\times \quad 26 \\
\hline
20592 \longrightarrow 6 \times 3432 \\
\end{array}
\]

\[
= 6 \times (3000+400+30+2)
\]

\[
= 18000+2400+180+12
\]

\[
= 20592
\]

\[
+ 68640 \longrightarrow 20 \times 3432
\]

\[
= 20 \times (3000+400+30+2)
\]

\[
= 60000+8000+600+40
\]

\[
= 68640
\]

\[
= 89232
\]

a. \[ 7382 \times 39 \]

b. \[ 6928 \times 72 \]

Sure! Let's solve each part of the problem step by step.

### Part a: [tex]$ 7382 \times 39 $[/tex]

1. Multiply 7382 by 9 (which is the units digit of 39):
[tex]\[
7382 \times 9 = 66438
\][/tex]

2. Multiply 7382 by 30 (which is the tens digit of 39, note that it's actually 3, but because it's in the tens place we multiply by 30):
[tex]\[
7382 \times 30 = 221460
\][/tex]

3. Add the two results:
[tex]\[
66438 + 221460 = 287898
\][/tex]

So, [tex]$ 7382 \times 39 = 287898 $[/tex].

### Part b: [tex]$ 6928 \times 72 $[/tex]

1. Multiply 6928 by 2 (which is the units digit of 72):
[tex]\[
6928 \times 2 = 13856
\][/tex]

2. Multiply 6928 by 70 (which is the tens digit of 72, note that it's actually 7, but because it's in the tens place we multiply by 70):
[tex]\[
6928 \times 70 = 484960
\][/tex]

3. Add the two results:
[tex]\[
13856 + 484960 = 498816
\][/tex]

So, [tex]$ 6928 \times 72 = 498816 $[/tex].

### Summary:

- [tex]$ 7382 \times 39 = 287898 $[/tex]
- [tex]$ 6928 \times 72 = 498816 $[/tex]

These are the step-by-step detailed solutions for each given problem.