SOLUTION: Gilbert makes frequent calls from country A to country B. His calling plan costs​ $5.00 per month plus 7¢ per minute for calls made to a landline and 17¢ per minute for calls
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Question 1110009: Gilbert makes frequent calls from country A to country B. His calling plan costs $5.00 per month plus 7¢ per minute for calls made to a landline and 17¢ per minute for calls made to a wireless number. One month his bill was $55.50. If he talked for a total of 350 min, how many minutes were to a landline and how many minutes to a wireless number? Answer by ikleyn(52786) (Show Source):
The given problem is equivalent to this system of 2 equations in 2 unknowns
x + y = 350, (1) (counting minutes)
7x + 17y = 5550 - 500 (2) (counting dollars and cents)
After substitution y = 350 - x from the first equation to the second equation, the system is reduced to a single equation for only ONE unknown
7x + 17*(350-x) = 5050,
7x + 17*350 - 17x = 5050,
-10x = 5050 - 17*350 = -900 ====> x = 90.
Answer. 90 landline minutes and the rest 350-90 = 260 wireless minutes.
Solved. // On the way, you learned on how the Substitution method works.
