Answer:
32 magazines
Step-by-step explanation:
If x is the number of subscriptions in December, then the number in January is x-7.
The relationship between the average price of magazines in the two months is ...
80/(x-7) -80/(x) = 0.70 . . . . . . . . .Jan price - Dec price = 0.70
80(x) -80(x -7) = 0.70(x)(x-7) . . . . multiply by the denominators
0.7x^2 -4.9x +560 = 0 . . . . . . . . put in standard form
x^2 -7x +800 = 0 . . . . . . . . . . . . . divide by 0.7
(x -32)(x +25) = 0 . . . . . . . . . . . . . factor
The product is zero when one of the factors is zero. x=32 or -25. The sensible solution for this problem is x=32.
The school library subscribed to 32 magazines in December.
