Answer:
The increase from $3.50 to $8.50 was 243%.
Explanation:
The increase from $3.50 to $12.00 was $8.50.
We need to compare this to the original $3.50 by writing the following ratio, evaluating it and converting the result to a percentage:
$8.50
--------- = 2.43
$3.50
Multiply this result by 100%: (100%)(2.43) = 243%
The increase from $3.50 to $8.50 was 243%.