show 7 + 21 written as a product of 2 factors

To express \( 7 + 21 \) as a product of two factors, we first calculate the sum:

\[
7 + 21 = 28
\]

Next, we can factor 28. One way to write it as a product of two factors is:

\[
28 = 4 \times 7
\]

So, \( 7 + 21 \) can be written as \( 4 \times 7 \). There are other pairs of factors as well, like \( 1 \times 28 \) or \( 2 \times 14 \).