Your phone plan charges 8 cents per min. for weekday/day calls. And 5 cents per min. For night/weekend calls. You had 220 minutes of calls.Your bill was $13.16

Question

How many night/weekend calls did you make

Answer 1

let there are x min. for weekday/day calls and y min. for night/weekend calls.So we will get two equations one for the total no. of calls which is 220 min.  and other for total bill which is $13.16 = 1316 cents (because we need all the amounts in same unit to make an equation)

 

             x+y= 220             (eqn 1. )  

===>     x=220- y 

 

         8x+5y = 13.16          ( eqn 2.)

      8(220-y) + 5y = 1316

      1760 -8y +5y = 1316

       1760 -3y = 1316

        1760 - 1316 =3y

               444 = 3y

                   y = 444/3 

                      = 148 min.

 

 

So 148 min. of night/weekend calls were made.