David buys 2 DVDs and 2 CDs in a shop and in total they cost £18. Ellie buys 3 DVDs and 2 CDs in the same shop and they cost £22.
Form two equations and solve to find the cost of each DVD and each CD.

Down below

Step-by-step explanation:

Let x be the cost for the DVD's

Let y be the cost of the CD's

Equations :

2x + 2y = 18   OR   y = (18 - 2x)/2

3x + 2y = 22

Substitution :

3x + 2[(18 - 2)/2] = 22

3x + 2(16/2) = 22

3x + 2(8) = 22

3x + 16 = 22

3x = 22 - 16

3x = 6

x = 6/3

x = 2

that's just the cost of the DVD though. now to find the CD's cost

Cost of CD's :

y = (18 - 2x)/2

y = [18 - 2(2)]/2

y = (18 - 4)/2

y = 14/2

y = 7

therefore 1 CD costs 7 pounds and 1 DVD costs 2 pounds

the answer   is 200

step-by-step explanation:

this is a problem about poisson probabilities.   i don't know if you've

already studied poisson distributions, or if you have a place to look

to read more about the subject.  

here's how you can see a poisson distribution coming.   when there are

a lot of events that may happen at any time (or any place), and when

you're counting how many of them happen at a particular time (or a

particular place), and each event is independent of the others, then

the result is a poisson distribution.   this is roughly true for the

chocolate chips; one chip being in a cookie has only a small effect on

the probability that another chip will be in the cookie.

once you know you have a poisson distribution, you know a lot.   there

is only one parameter to a poisson distribution, so if you know the

mean, you know everything.   the form of the distribution is

  probability of n chips = {[e^(-x)]*(x^n)} / (n! )

do i do it on a graph?

step-by-step explanation: