SOLUTION: Ok, my son is has a problem in Algebra, he is in the 9th grade. I can get the answer for him but he need to write it in algebra terms. I never took algebra in school, so if I can

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Question 569356: Ok, my son is has a problem in Algebra, he is in the 9th grade. I can get the answer for him but he need to write it in algebra terms. I never took algebra in school, so if I can tell you the question. can you please tell me how to write it in algebra terms.
Mike just got a phone bill for $27.60. he is charge $.07 per minute for local calls and $.20 for long distance calls. he talked for a total of 320 minutes. How many long distance minutes did he use?
It sounds just like a typical story problem and easy to solve but feel bad that I can't put it in Algebra form
Thanks so much,
Until Next time,
Sue
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
Mike just got a phone bill for $27.60. he is charged $.07 per minute for local calls and $.20 for long distance calls. he talked for a total of 320 minutes.
How many long distance minutes did he use?
:
We need two equation to solve two unknowns, we are going to use substitution to solve this
Let x = no. of local minutes
Let y = no. of L.D minutes
;
x + y = 320; (total minutes equation
x = (320-y); this form for substitution
:
.07x + .20y = 27.60; (total cost equation)
Replace x with (320-y)
.07(320-y) + .20y = 27.60
22.4 - .07y + .20y = 27.60; (multiplied what's inside the brackets)
-.07y +.20y = 27.60 - 22.4
.13y = 5.20
y =
y = 40 minutes of L.D calls which is answer they want
:
then in order to check our solution
using x + y = 320
x + 40 = 320
x = 320 - 40
x = 280 minutes of Local calls
:
:
Confirm this in the equation; .07x + .20y = 27.60
.07(280) + .20(40) =
19.60 + 8.00 = 27.60;