Answer:
74
Explanation:
Multiply 16 (packs of batteries) by 4 (amount in each package) to get 64,

⇒ 6 * 4 = 24; 10 * 4 = 40; 24 + 40 = 64
then add 10 (batteries she had before buying more).
64 + 10 = 74.
Now Jenny has 74 batteries for her school project.