A)
Let X be the food expenditure of a family.
Let the population mean of an expenditure of a family be.
Let the population standard deviation of an expenditure of a family be.
The proportion families spend more than $30 but less than $490 per month on food is,
It is helpful to estimate quotients when the number is very big.
Answer:
-3<x<3
Step-by-step explanation:
let y=0
0=x^2-9
0=(x+3)(x-3)
x=-3 and x=+3
