Harold has $20 to spend he decides to buy a shirt for $15.95 to spend the rest on packs of gum. If each pack cost $1.99 how many packs of gum can Harold buy.

Harold spent $15.95 on a shirt, so he has $20 - $15.95 = $4.05 left to spend on gum.

Each pack of gum costs $1.99, so Harold can buy $4.05 / $1.99 ≈ 2 packs of gum.
Therefore, Harold can buy 2 packs of gum.