he cost of a protein bar increased from $2.50 to $2.80. The percent increase in the $2.80 rate was how much?

$2.80 - 2.50 = $0.30

0.3 / 2.5 = 0.12 = 12%

To find the percent increase, you can use the following formula:

Percent increase = ((new value - old value) / old value) * 100

In this case, the old value (the initial price of the protein bar) is $2.50, and the new value (the increased price) is $2.80.

Applying the formula:

Percent increase = (($2.80 - $2.50) / $2.50) * 100

Percent increase = ($0.30 / $2.50) * 100

Percent increase = 0.12 * 100

Therefore, the percent increase in the price of the protein bar is 12%.