Stan took lily to his friends restaurant on a date the friend told the waiter to remove the $12 desert from stabs bill Stan tipped the waiter 20 percent on the reduced bill which was a $15 tip fill in the blanks to write an equation that will determine the amount of the original bill b.

Let's assume that the original bill amount is represented by b.

According to the given information, the friend told the waiter to remove the $12 dessert from Stan's bill. This means that the original bill is reduced by $12, so the new bill amount becomes b - $12.

Next, it is mentioned that Stan tipped the waiter 20 percent on the reduced bill, which was a $15 tip. This can be represented as:

0.2 * (b - $12) = $15

Therefore, the equation that will determine the amount of the original bill b is:

0.2 * (b - $12) = $15