We are given that Serenity pays a flat cost of $64.50 per month and also pays $4 dollars per gigabyte. She also wants to keep her bill under $70 per month.
Explanation
If we let the number of gigabytes she can use be x, we will have that;
[tex]cost\text{ of data =}4x[/tex]Therefore,
The cost of her cell phone plan can be expressed with the equation
[tex]4x+64.50[/tex]Since Serenity also wants to keep her bill under $70 per month, we will have;
[tex]4x+64.50<70[/tex]Solving the above inequality for x, we will then give the maximum whole number of gigabytes of data she can use while staying within her budget.
[tex]\begin{gathered} 4x+64.5<70 \\ \mathrm{Subtract\:}64.5\mathrm{\:from\:both\:sides} \\ 4x+64.5-64.5<70-64.5 \\ simplify \\ 4x<5.5 \\ Divide\text{ }both\text{ }sides\text{ }by\text{ }4 \\ \frac{4x}{4}<\frac{5.5}{4} \\ x<1.375 \\ therefore,\text{ we will round down to 1} \\ x\approx1 \end{gathered}[/tex]Answer: 1 gigabyte
