It cost 3.99 for 25 oz and 6.99 for 90oz which is better and why

First is to find out which price is lower for each when it's only for one ounce.

1) 3.99 / 25 = x / 1

Cross multiply.

3.99 = 25x

Divide both sides by 25.

0.1596 = x

Round to the nearest cent.

$0.16 per ounce

2) 6.99 / 90 = x / 1

Cross multiply the fractions.

6.99 = 90x

Divide both sides by 90.

0.0776667 = x

Round to the nearest cent.

$0.08 per ounce.

6.99 for 90oz is better because it is cheaper by 8 cents per ounce.