Question

Susan is writing a linear equation for the cost of her cell phone plan. In the first month, she talks for 52 minutes and is charged $19.41. In the second month, she talks for 380 minutes and is charged $45.65.
A) How much money does Susan's cell phone company charge for each minute?
B) Write an equation that Susan can use to determine the cost of her cell phone plan, y, as it relates to the number of minutes used, x.

Answer 1

$\frac{f(b)-f(a)}{b-a}\\\frac{45.65-19.41}{380-52}\\\frac{26.24}{328}\\0.08\\\\19.41-52*0.08\\19.41-4.16\\15.25\\\\y=0.08x+15.25$

Eight cents per minute.

y=0.08x+15.25