(1) let "r" denote number of rabbits, "c" number of chickens
Set up the equations:

Answer: There are 575 rabbits and 425 chickens
(2) m - number of Mike's stamps, a - number of Andrew's stamps.
Set up equations:

Answer: Mike has 48 stamps. Andrew has 12 stamps.
Step-by-step explanation:
you multiply the number of lemonades by 1.80 because you're just basically adding 1.80 from each lemonade you sell
Answer:
The sample size needed is 2401.
Step-by-step explanation:
In a sample with a number n of people surveyed with a probability of a success of
, and a confidence level of
, we have the following confidence interval of proportions.

In which
z is the zscore that has a pvalue of
.
The margin of error of the interval is:

95% confidence level
So
, z is the value of Z that has a pvalue of
, so
.
Estimate the sample size needed if no estimate of p is available so that the confidence interval will have a margin of error of 0.02.
We have to find n, for which M = 0.02.
There is no estimate of p available, so we use 






The sample size needed is 2401.
The intersection of two planes is a line. That's not necessarily the definition of a line, but that's probably what they're looking for.
Answer: line
The first one is 810
The second is -120