Acereal bar is sold individually for $2.40 or in packs of 4 for $8 per pack. roxie wants to buy exactly 38 cereal bars. what is the least amount of money that roxie can spend on cereal bars?

If Roxie were to buy the cereal bars individually, it would be
38 x $2.40 = $91.20
If she were to buy them in packs, she would need to buy 9 packs along with 2 individual bars (because there are 4 in each pack, 4x9=36 and adding 2 more would make it 38) 
9 x $8  = $72
2  x $2.40 = $4.80
$72 + $4.80 = $76.80

The least amount of money Roxie can spend is $76.80 by buying the cereal bars in packs.