Answer
Find out the which system of equations could be used to determine the number of hours charged at the day rate (d) and at the night rate (n) .
To proof
As given in the question
Let us assume that the number of hours charged at the day rate = d
Let us assume that the number of hours charged at the night rate = n
An online data base charges $25 an hour during the day and $12.50 an hour at night. If a research company paid $250 for 12 hours of use.
Total working hour in a company including day and night be 12 hours .
than the equation become in the form
d + n = 12
also
An online data base charges $25 an hour during the day
$12.50 an hour at night.
If a research company paid $250 for 12 hours of use.
than the equation becomes
25d + 12.50n = 250
than the two equation are
d + n = 12 , 25d + 12.50n = 250
multiply first by 25 and subtracted from 25d + 12.50n = 250
25d - 25d + 12.50n - 25n = 250 - 300
12.5 n = 50
n = 4hours
put this in the d + n = 12
d + 4 =12
d = 12-4
d = 8 hours
Therefore the number of hours charged at the day rate is 8 hours and at the night rate is 4hours .
Hence proved
