Answer:
the greatest common factor of 12 and 18 is 6.
Step-by-step explanation
GCF of 18 and 32 = 2.
GCF of 21 and 84 = 21.
GCF of 36 and 100 = 4.
GCF of 12 and 48 = 12.
GCF of 18 and 35 = 1.
GCF of 18 and 63 = 9.
GCF of 48 and 56 = 8.
Selection C is appropriate.
_____
A. The population is constant at 8.
B. The population is constant at 24.
C. Matches the problem description.
D. The initial population is 24 and after 1 hour is 72.
Answer:
y = ac / (a - b - c)
Step-by-step explanation:
y(a - b) = c(y + a)
Distribute
ay - by = cy + ac
Subtract cy from both sides
ay - by - cy = ac
Factor out y
y(a - b - c) = ac
Divide both sides by (a - b - c)
y = ac / (a - b - c)
52+23=75
10+78=88
88+75=163
that's one way
All the numbers in this range can be written as

with

and

. Construct a table like so (see attached; apparently the environment for constructing tables isn't supported on this site...)
so that each entry in the table corresponds to the sum of the tens digit (row) and the ones digit (column). Now, you want to find the numbers whose digits add to perfect squares, which occurs when the sum of the digits is either of 1, 4, 9, or 16. You'll notice that this happens along some diagonals.
For each number that occupies an entire diagonal in the table, it's easy to see that that number

shows up

times in the table, so there is one instance of 1, four of 4, and nine of 9. Meanwhile, 16 shows up only twice due to the constraints of the table.
So there are 16 instances of two digit numbers between 10 and 92 whose digits add to perfect squares.