Currently, tony has $60 and his sister has $40. Tony gets an allowance of $5 each week, while his sister gets an allowance of $10 each week.

Question

Write an equation to represent how much money each person has after x weeks

Answer 1

Let x = number of weeks   [note: x=0 to start]

 

Let T(x) be the amount that Tony has after x weeks

Let S(x) be the amount that sister has after x weeks

 

"Currently, tony has $60"     means T(0) = $60

"Currently, . . .his sister has $40"    means S(0) = $40

 

Note:  (dollars per week)*(number of weeks) = dollars                [weeks cancel out]

 

For Tony:     T(x) = $60 + $5x

For sister:    S(x) = $40 + $4x

 

Note: equations are usually written with highest power of variables first, so:

 

                  T(x) = 5x + 60

                  S(x) = 4x + 40

Answer 2

We start with T(x) = , because that's the amount of money Tony has after any given week.

He starts off with $60 on hand, that means we now currently have:

T(x) = 60

Each week, he gets $5, so that means the 5 is our slope with weeks being our variable:

T(x) = 5x + 60

 

We can have s(x) be his sister, and you can follow the same methodology to find her equation.