Number of weekend minutes used: x Number of weekday minutes used: y
This month Nick was billed for 643 minutes: (1) x+y=643
The charge for these minutes was $35.44 Telephone company charges $0.04 per minute for weekend calls (x) and $0.08 per minute for calls made on weekdays (y) (2) 0.04x+0.08y=35.44
We have a system of 2 equations and 2 unkowns: (1) x+y=643 (2) 0.04x+0.08y=35.44
Using the method of substitution Isolating x from the first equation: (1) x+y-y=643-y (3) x=643-y
Replacing x by 643-y in the second equation (2) 0.04x+0.08y=35.44 0.04(643-y)+0.08y=35.44 25.72-0.04y+0.08y=35.44 0.04y+25.72=35.44
Solving for y: 0.04y+25.72-25.72=35.44-25.72 0.04y=9.72
Dividing both sides of the equation by 0.04: 0.04y/0.04=9.72/0.04 y=243
Replacing y by 243 in the equation (3) (3) x=643-y x=643-243 x=400
Answers: The number of weekends minutes used was 400 The number of weekdays minutes used was 243
