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.

He must use  3 GB or less

Step-by-step 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

whats the

not only in mathematics, scientific proof also are required in the other field of science. also maths proofs are of particular structure, containing steps and logics. so proving is like doing science, it is science. that's why it is important to prove. 

an inaccurate proof leads to errors, or stating results that are not accurate.  which wil mess the probelm up you dont want this