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Mary has a budget of $40 per month to spend on movies. She made a table showing the total amount of movie money she will have left after seeing the given number of movies.


Number of movies 0 1 2 3

Total amount of movie money left ($) 40 29 18 7

Which equation, in standard form, represents the relationship between the number of movies, x, and the amount of movie money Mary will have left, y?


11x−y= 4011x−y= 40


11x + y = 40


x + 11y = 40


x−11y= 40

Verified Answer :

11x + y = 40 is the answer

Answer

11x + y = 40

Explanation

We know from our table that when Mary has seen 0 movies her budget is $40, so our first point is (0, 40)

We also know that when she has seen 1 movie her budget is $29, so our second point is (1, 29)

To find our line equation, we first need to find the slope between our points. To do it, we are using the slope formula: \(m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}\)

where

\((x_{1},y_{1})\) are the coordinates of the first point

\((x_{2},y_{2})\) are the coordinates of the second point

We can infer from our points that \(x_{1}=0\), \(y_{1}=40\), \(x_{2}=1\), and \(y_{2}=29\). So let's replace those values in our formula to find \(m\)

\(m=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}\)

\(m=\frac{29-40}{1-0}\)

\(m=-11\)

Now that we have our slope, we can use the point slope formula to find the equation of our line

\(y-y_{1}=m(x-x_{1})\)

\(y-40=-11(x-0)\)

\(y-40=-11x\)

\(y=-11x+40\)

\(y+11x=40\)

\(11x+y=40\)