Question

Joe’s cell phone costs him $21 per month plus $3 for every 1GB of data downloaded. What is the limit to the number of GBs he can download to stay within his monthly budget of $30.

Answer 1

He must use 3 GB or less

Explanation:

Total cost = flat fee + number of GB * charge per GB

We know he must stay under 30 dollars so change the equals to less than or equal to (the opening facing the 30) and replace the total cost with 30

30≥ flat fee + number of GB * charge per GB

We know the flat fee is 21 and the charge per GB is 3

30≥ 21 + number of GB * 3

Subtract 21 from each side

30-21 ≥ 21-21 + number of GB * 3

9≥number of GB * 3

Divide by 3

9/3 ≥ number of GB * 3/3

3≥ number of GB

He must use 3 GB or less