Alan

Arrange them in ascending order.  Then, because there is an even number of them, take the two middle ones (i.e. the sixth and seventh) and form the mean of those two to generate the median.

Go to the HELP menu.  There is a CONTACT EMAIL section.  However, I suspect Andre already knows.  He's probably in the middle of modifying the calculator in some way!

Here's the answer to part b:

You should check this carefully, as I did it rather hurriedly!

You can look at this question as follows:

"Write the augmented matrix ..."

As follows:

Let b = baseball, k = basketball, t = tennis ball, s = soccer ball.

Then you have the following four equations:

b + k = 240              (1)

t + s = 500               (2)

s - k + t = 455          (3)

b + t = 215               (4)

From (1) we have  k = 240 - b.  Put this into (3):

s - 240 + b + t = 455  Rewrite as:

s + t + b = 695        (5)

Use (2) in (5) to get  500 + b = 695   so that  b = 195

Use b in (4) to get  195 + t = 215    so t = 20

Use t in (2) to get   20 + s = 500  so s = 480

The socer ball is worth 480.

I get the following:

Yes, the solve function seems to be disabled at present.  Don't know why.  With luck it will be up and running again soon!

This is \(\sum_{i=1}^34\times(\frac{1}{2})^{i-1}=4\times 1+4\times \frac{1}{2}+4\times \frac{1}{4}\)

You should be able to finish from here.