Question

Easy to Find, a computer data base, charges $30/h during peak hours to access its records. The charge during off-peak hours is $12/h. Indigo Research was billed $876.00 last month for 40 hours of access time. Using a system of equations, find the number of hours charged for usage during peak times.

Answer 1

p + o = 40 (where p = peak and o= off-peak)
30p + 12o = 876
This can be done using elimination or substitution.
I will do elimination.

Multiply the first equation by -12. This will 'eliminate' the variable o.
-12p -12o = - 480
30p + 12o = 876

Now add the two equations together.
18p = 396
Divide both sides by 18
p = 22
40 - 22 = 18
Peak hrs. = 22
Off-Peak = 18
CHECK 22(30) + 18(12) = $876