Answer:
He needs to sell 25 pieces of artwork.
Explanation:
$500 for an oil painting.
$300 for a charcoal sketch.
56 pieces of artwork total.
$20,000 goal.
500 + 300
= 800
$800 for 1 oil painting and 1 charcoal sketch.
20,000 ÷ 800
= 25
He needs to sell 25 pieces of artwork to make $20,000.