There are two conditions :
1) If data consumed is less than or equal to 2 GB.
2) if data consumed is more than 2 GB.
Change in 1st condition is constant i.e $50.
Now, charge in 2nd condition is given by :
![C=15x+50](https://img.qammunity.org/2021/formulas/mathematics/high-school/eivtbqg4h677rrikaleen45yxbmq0lljot.png)
So, money she have to pay in a month where she used ent over by x GB is :
![C(x) = \$50\ , \ 0 \leq x \leq 2\\or\\C(x ) = \$\ (50+15x )\ ,\ x \geq 3](https://img.qammunity.org/2021/formulas/mathematics/high-school/ij96jh5lnb7merovkziml2joiztmipqn6r.png)
Hence, this is the required solution.