20. A backpack that normally sells for $39 is on sale for 33% off. Find the amount of the discount and the sale price.
21. In August, the Simons' water bill was $48. In September, it was 15%
lower. What was the Simons' water bill in September?
22. A gallery owner purchased a very old painting for $3,000. The painting
sells at a 325% increase in price. What is the retail price of the
painting?

$26.13 sale price. $12.87 discount amount

Step-by-step explanation:

Discount is $39 * 33% (.33)= $12.87

Sale price is $39-$12.87=$26.13

the function makes a strait line horizontally with no x intercept but a y intercept at 9.

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for