Answer:
"The demand was so high for the concert tickets that the concert manager posted a tweet on social media saying that the quantity they had, wasn't enough for the amount of people that wanted to buy concert tickets."
Explanation:
Quantity in economics is the amount in total of the product there is.
Demand in economics is how much the consumer is willing to buy the product that is being sold.
A sentence using the two words quantity and demand about concert tickets would look something like this: "The demand was so high for the concert tickets, that the concert manager posted a tweet on social media saying that the quantity they had, wasn't enough for the amount of people that wanted to buy some of the concert tickets."
Hope this helps.