A= 1.142 m/hr
Width of beach at 8 p.m. = 36 m
Width of beach at 3 a.m. = (36-8) m =28 m
Average change in width(A) = change in width (Width of beach at 8 p.m.-Width of beach at 3 a.m.0/ time in hours
A= ( 36-28)/ 7
A= 8/7 m/hr
A = 1.142 m /hr
Let
be the price of an adult ticket, and
the price of a child ticket.
The sentence "Three adults and four children must pay $122 for tickets" translates to 
The sentence "Two adults and three children must pay $87" translates to 
Which leads to the linear system

You can solve this system as you prefer, for example you can multiply the first equation by 2 and the second by 3 to get

Now subtract the first from the second:

Now plug this value for c in any of the equations, for example the first:

Answer:
B
Step-by-step explanation:

Answer:
y ≥ 3x
Possible solution: x=1, y=3
Step-by-step explanation:
Since Henry has atleast 3 times as much money as Deb
y=3x
y must always be greater than or equal to 3x
if x=1 y=3
Answer:
She has 15 more purple rocks than blue.
Step-by-step explanation:
purple= 2/3 of all rocks
blue= 3/4 of all rocks that aren't purple
silver= 3 (or 1/4 of all rocks that aren't purple)
if 3 (silver) is 1/4 of all rocks that aren't purple, blue (3/4) is 3x3=9
if purple is 2/3 of all rocks, blue and silver are 1/3 of all rocks
so 1/3 of all rocks would be 9+3=12
if 1/3=12, then 2/3 (purple)=24
-----
At this point:
purple=24
blue=9
silver=3
-----
purple (24) - blue (9) =15
She has 15 more purple rocks than she does blue.