The cost of a slice of pepperoni pizza is $7, and the cost of a slice of supreme pizza is $5.
The cost per slice of each type of pizza can be determined by dividing the total dollar amount by the number of slices sold. For pepperoni pizza on Day 1, the cost per slice is calculated as $3,730 / 500 = $7. Similarly, for supreme pizza on Day 1, the cost per slice is $3,730 / 620 = $6.
The average cost for each pizza type is then calculated by averaging the costs for both days. For pepperoni pizza, the average cost is ($7 + $7) / 2 = $7. For supreme pizza, the average cost is ($6 + $5) / 2 = $5.50.
Since the cost should be a whole number, and considering that the average cost is closer to $5 than $6, it can be reasonably concluded that the cost of a slice of supreme pizza is $5. Therefore, the final answer is $7 for a slice of pepperoni pizza and $5 for a slice of supreme pizza, based on the average costs calculated from the total dollar amounts and slices sold over the two days.