The binomial expansion:

a = 2y, b = 4 x^3, n = 4
( x )^3k = x^ 9
k = 3


Answer: the coefficient is
512.
If the dots are going to the right, it's positive. If they're going to the left, they're negative.
Answer:
set mary is x years old, and helen is y years old.
first sentence:x=2y
second one:4(y-8)=x+4
bring x=2y in 4(y-8)=x+4
=>4y-32=2y+4
=>2y=36
=>y=18
=>x=36
mary:36
helen:18
13/52. There are 13 red hearts in a deck of 52 cards.