Question

A phone company charges $0.06 per minute for local calls and $0.15 per minute for international calls. When your bill comes, it states that you accumulated 852 minutes with a charge of $69.84. Write and solve a system of linear equations to find the number of local and international minutes used.

Answer 1

Let
 x = number of minutes of local calls.
 y = number of minutes of international calls.
 By writing the system of equations we have:
 0.06x + 0.15y = 69.84
 x + y = 852
 Solving the system
 Clear y from equation two
 y = 852-x
 Replace y in equation 1
 0.06x + 0.15 (852-x) = 69.84
 Clear x
 0.06x + 127.8 - 0.15x = 69.84
 127.8 - 69.84 = 0.15x -0.06x
 57.96 = 0.09x
 x = 57.96 / 0.09 = 644
 x = 644
 Replace x in any of the two equations and clear y:
 x + y = 852
 y = 852-644
 y = 208
 answer
 number of minutes of local calls = 644
 number of minutes of international calls = 208