Question 1195736
x = number of text messages
y = number of minutes of voice calls.
the equation is .15x + .08y = 25
when x = 0, y = 25/.08 = 312.5.
when y = 0, x = 25/.15 = 166.67, rounded to 2 decimal places.
you can pick any value of x between 0 and 166.67 and you will get the corresponding value of y.
you can pick any value of y between 0 and 312.5 and you will get the corresponding value of y.
the assumption here is that you spend exactly 25 dollars.
for example, if x=100, then the equation becomes .15 * 100 + .08 * y = 25
solve for y to get y = (25  - .15 * 100) / .08 = 125
as long as the total has to be 25, then y = 125 when x = 100.


here's what the graph looks like.
<img src = "http://theo.x10hosting.com/2022/072501.jpg">


let me know if you have any questions.
theo