Question

kristen gets a 20 dollar bill each time she baby sits and a 5 dollar bill each time she mows the lawn. she wants to know what combination of these bills could add up to 85 dollars. x = 5 dollar billsy = 2o dollar bills

Answer 1

SOLUTION:

Step 1:

$\begin{gathered} 20y\text{ + 5x = 85} \\ 20y\text{ = 85 - 5x} \\ \text{Dividing both sides by 20} \\ y\text{ = }\frac{85}{20}\text{ - }\frac{5x}{20} \\ y\text{ = }\frac{85\text{ -5x}}{20} \end{gathered}$

Step 2:

To find the domain where y is a function of x, we simply substitute the values of x and as many that give whole numbers are the domain;

When x = 1, y = 4

x = 5, y = 3

x = 9, y = 2

x = 13, y = 1

x = 17, y = 0

Domain {1,5,9,13,17}, missing values gives fractions and currency notes can not be fraction but whole number.