When making a telephone call using a calling card a call las

When making a telephone call using a calling card, a call lasting 3 minutes cost $1.20. A call lasting 13 minutes
cost $3.70. Let y be the cost of making a call lasting x minutes using a calling card. Write a linear equation that
relates the cost of a making a call, y, to the time x.

Solution

Let y be the cost of making a call lasting x minutes using a calling car

a call lasting 3 minutes cost $1.20 =>(x₁,y₁)=(3,1.2)

a call lasting 13 minutes cost $3.70 =>(x₂,y₂)=(13,3.7)

linear equation by 2 point form is

y -y₁=[(y₂-y₁)_/(x2-x1)](x-x1)

y -1.2=[(3.7-1.2)_/(13-3)](x-3)

y -1.2=[2.5_/10](x-3)

y -1.2=0.25(x-3)

y -1.2=0.25x-0.75

y=0.25x -0.75+1.2

y =0.25x +0.45

linear equation that relates the cost of a making a call, y, to the time x. is y =0.25x +0.45