MATH
posted by jennifer on .
Furnace repairs
A repairman purchased several furnace blower motors for a total cost of $210. If is cost per motor had been $5 less, he could have purchased one additional motor. How many motors did he buy at the regular rate?
Please help

regular rate = r
discount rate = (r5)
number bought = n
number that would have been bought = (n+1)
so
210 = r n
and
210 = (r5)(n+1) = r n + r  5 n 5
from the first equation r = 210/n
then the second
215 = (210/n)n +210/n 5 n
5 = 210/n 5 n
5 n = 210 5 n^2
n^2 + n  42 = 0
(n8)(n+7)=0
n = 8 
sorry
(n+7)(n6) = 0
n = 6 
check
r = 210/n = 35
r5 = 30
n+1 = 7
30 * 7 = 210 check 
thank you very much

HELP!!!!!I need a better explination.