Question 392083
Nathan's monthly electric bill includes a fixed service charge and an additional 
charge for the number of kilowatt-hours (kwh) of electricity used.
 One bill, including a charge for 595 kwh of electricity, is $61.72.
 Another bill, including a charge for 650 kwh, is $67.11.
 Find the fixed charge and the cost per kilowatt-hour.
:
Let x = the fixed charge
Let y = the cost/kwh
:
An equation for each month
x + 650y = 67.11
x + 595y = 61.72
--------------------subtracting eliminate x find y
55y = 5.39
y = {{{5.39/55}}}
y = $.098 per kwh
:
Find the fixed cost (x)
x + 650(.098) = 67.11
x + 63.70 = 67.11
x = 67.11 - 63.70
x = $3.41
:
Check this solution in the 2nd equation
3.41 + 595(.098) = 
3.41 + 58.31 = 61.72
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