First we should change these mixed numbers into improper fractions:
[tex]12 \frac{4}{9}= \frac{112}{9} [/tex]
[tex]1 \frac{7}{9}= \frac{16}{9} [/tex]
We can find the number of crates used by dividing the total amount of electrical supplies by the amount that each crate can hold:
[tex] \frac{112}{9} [/tex] / [tex] \frac{16}{9}=\frac{112}{9}[/tex] * [tex] \frac{9}{16} = \frac{1,008}{144}=7 [/tex]
So now we know that Otto used 7 crates.