Which is more? 1 gallon or 8 liters?

8 litres is roughly equivalent to 2 gallons, so 8 litres would be a lot more than 1 gallon. Hope this helps! :)

the most expensive painting is $10000

Step-by-step explanation:

Let x represent the amount for which the first painting was sold. One painting is sold for 5 times the amount of a second. This means that

x = 5y

The third was sold for $1500. If the total sale was for $13500, it means that

5y + y + 1500 = 13500

6y + 1500 = 13500

6y = 13500 - 1500 = 12000

y = 12000/6 = 2000

x = 5y = 5× 2000 = 10000