Question

Susan is putting money into a savings account. She starts with $750 in the savings account, and each week she adds $40.

Let S represent the total amount of money in the savings account (in dollars), and let W
represent the number of weeks Susan has been adding money. Write an equation relating S to W. Then use this equation to find the total amount of money in the savings account after 16 weeks.

Answer 1

s=$750+$40w
s=$750+$40(16)
s=$750+640
s=$1,390

Answer 2

To model this situation, we are going to use the standard linear function: $y=mx+b$.

1. Since S represent the total amount of money in the savings account, $y=S$. We also know that each week she adds $40 to her account, so the slope of our linear equation will be $40W$; therefore, $m=40W$. Since she started her account with $750, $b=750$. 
Lets replace those values in our linear function:
$y=mx+b$
$S=40W+750$

We can conclude that equation that models this situation is: $S=40W+750$

2. Now to find the total amount after 16 weeks, we just need to replace $W$ with 16 in our equation and simplify:
$S=40(16)+750$
$S=640+750$
$S=1390$

We can conclude that the amount of money in her account after 16 weeks is $1390