Answer: $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
Answer:
b
Step-by-step explanation:
Answer:
The smaller number is 4
Step-by-step explanation:
Larger number = x
Smaller number = y
Write 2 equations
y + 6 = x
2x = 5y
Substitute x in the first equation to the second equation
2(y + 6) = 5y
Multiply 2(y + 6)
2y + 12 = 5y
Subtract 2y from both sides of the equation
12 = 3y
Divide both sides of the equation by 3
y = 4
x = y + 6 = 4 + 6 = 10
The smaller number is 4
Hope this helps :)