Given:
Cell Phone Service, x=$36.45 per month
Landline Phone Service, y= $30.11 per month
Cable TV Service, z=$57.43 per month
Internet Service, p= $37.32 per month
The price for a package of all services, P=$131.59.
The total price of services before purchasing the package is,
[tex]T=36.45+30.11+57.43+37.32=161.31[/tex]Now, the percentage decrease by purchasing the package is,
[tex]\begin{gathered} \text{Percentage}=\frac{T-P}{T}\times100 \\ =\frac{161.31-131.59}{161.31}\times100 \\ =18.4 \end{gathered}[/tex]Therefore, the percentage decrease by purchasing the package is 18.4%.