Answer:
$3.63
Step-by-step explanation:
A 10-minute call to France cost $3.19.
[tex](x_1,y_1)=(10,3.19)[/tex]
A 15-minute call to France costs $4.29.
[tex](x_2,y_2)=(15,4.29)[/tex]
Now we will use two point slope form
[tex]y-y_1=\frac{y_2-y_1}{x_2-x_1}(x-x_1)[/tex]
Substitute the values :
[tex]y-3.19=\frac{4.29-3.19}{15-10}(x-10)[/tex]
[tex]y-3.19=0.22(x-10)[/tex]
[tex]y-3.19=0.22x-2.2[/tex]
[tex]y=0.22x-2.2+3.19[/tex]
[tex]y=0.22x+0.99[/tex]
y is the cost and x is the number of minutes
Now we are suppose to find cost of a 12-minute call to France
Substitute x = 12
[tex]y=0.22(12)+0.99[/tex]
[tex]y=3.63[/tex]
Hence the cost of a 12-minute call to France is $3.63