need help to answer algebraic word problem for 7th grader

Question

please help answer the questions

 

Mr Yangs ISP charges $10 per month for 8 hours. Plus $.50 per additional hour. If he spent 18.50 on his monthly bill how many additional hours did he spend online?

Answer 1

Mel,

 

Assume Mr. Yang used t hrs additional time

 

So his total cost is $10 + 0.50*t

 

Since total cost is $18.50

 

10 + .5*t = 18.5

.5t = 8.5

t = 17

 

He spends 17 additional hrs.

Answer 2

Suppose x is the total number of hours.

 

The base charge would be $10 plus $.50 for every hour more than 8.  So the number of extra hours charged for would be x - 8.

 

Then the bill would be 10 + 0.5 (x - 8).

 

So set that equal to 18.50 and solve for x.

 

10 + 0.5 (x - 8) = 18.50

 

Subtract 10 from both sides.

0.5 (x - 8) = 8.50

 

Divide both sides by 0.5

x - 8 = 17

 

Add 8 to both sides

x = 25

 

Since x was the TOTAL number of hours, the additional hours would be x - 8, or 17