Answer
$18.5\text{ inches}$
Work Step by Step
There are eight $2\frac{5}{16}$-inch spaces between the first and last rivets.
Thus, the distance between the first and last rivets is:
$\require{cancel}
=8 \times 2\frac{5}{16}
\\=8 \times \frac{16(2)+5}{16}
\\=8 \times \frac{37}{16}
\\=\cancel{8} \times \frac{37}{\cancel{16}2}
\\=\frac{37}{2}
\\=18.5\text{ inches}$
