F leonard bought 2 packs of batteries for x amount of dollars, how many packs of batteries could he purchase for $5.00 at the same rate

1.

The rate at which Leonard bought was 2 packs per x dollars,

that is his buying rate was (2 packs) / (x dollars) = 2/x (p/$)

2.

with 1 $ Leonard buys 2/x packs

then

with 5 $ Leonard buys (2/x) * 5 = 10/x packs.

Answer: 10/x packs