The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). The remaining credit after 38 minutes of calls is $ 25.06, and the remaining credit after 69 minutes of calls is $21.03. What is the remaining credit after 80 minutes of calls?

$19.6

Step-by-step explanation:

Linear function: f(x)=mx+c

, where  m= rate of change in f(x) with respect to x.

c = Initial value.

Let c = Initial value of card , m= Charge per minute

x= Number of minutes calling time.

Then, 25.06= 38m+c   (i)

21.03=69m+c (ii)

Eliminate (ii) from (i)

Put m in (i) , we get

i.e. f(x)=-0.13x+30

if x=80 then

f(80)= -0.13(80)+30

=-10.4+30

=19.6

Hence, the remaining credit after 80 minutes of calls = $19.6

1. x> -5

2. x< 8

step-by-step explanation:

1. 2x> -10

divide by 2 from both sides of equation.

2x/2> -10/2

simplify, to find the answer.

-10/2=-5

x> -5 is the correct answer.

2. 3x< 24

divide by 3 from both sides of equation.

3x/3< 24/3

simplify, to find the answer.

24/3=8

x< 8 is the correct answer.

i hope this you, and have a wonderful day!