Math problem that I need some help with *HARD ONE*?

Question

I uploaded a screenshot to the internet, It's multiple choice.

http://www.scribd.com/doc/4979947/screenshot-9

Answer 1

c = 30t +20

1) when t= 8months

c= 30x8 + 20 = 260

2) when c= $90  

90 = 30t +20

30t = 70

t = 70/30 = 7/3 = 2 1/3 (option c)

3)option b

Answer 2

okay frist one is 260$

secound - C

tthird- B

Answer 3

Okay, here's how I did it:

The beginning is pretty easy because they already give us the formula which is c = 30t + 20 in which c = cost and t = the number of months. So the cost for 8 months of service is equal to

30 * 8 + 20 which gives us:

260$ (total cost)

For the second question now. We will have to replace C by 90.

so it gives us

90 = 30t + 20

now we resolve the equation

90 -20 = 30t + 20 -20

70 = 30t

now we divide by 30 to have the value of 1 t

70/30 = 30t/30

2.3333 = t

So the good answer is C, the customer can pay for 2 and 1/3 months.

finally, the good graph is the B one, because it starts at a initial cost of 20 and goes up 30 each month.

Hope I helped!

Answer 4

c=30t +20

cost for 8 months... substitute for t=8

c=30 x 8 +20

c=240 + 20=260

if only 90 dollars avail find t, set c=90

90= 30t +20

subtract 20 from both sides

70=30t

solve for t

t=70/30= 2.33= 2 1/3 or answer c

graph of c=30t +20 which is in the form y=mx + b where m= slope= 30 and b= y intercept which is 20 correct answer=b

Answer 5

The answer is "b" x*x