Alan

Here are my attempts:

.

Like so:

Look at it this way:

Label the people from 1 to 9 then continue with letters A to N.

Pair them in the following way:

13      24

35      46

57      68

79      8A

9B      AC

BD     CE

DF     EG

FH     GI

HJ      IK

JL      KM

LN      M2

N1

23 pairings with each label occurring exactly twice.

This set of pairings is not unique of course.

To find (a) calculate  360 - (70 + 90 + 115)

Use the same approach on the others. 

See https://web2.0calc.com/questions/probability_71#r2

These have been answered already; the first one in great detail. It’s no good just repeating the question. You need to be more precise in stating what you don’t understand and where you start to lose the plot. 

If your teacher wants the result in a different form you need to say what that different form is.

b²*(b + 4) is      b²*b + b²*4           or             b³ + 4b²

Have a look at the step by step approach I've just posted to your previous question, and try the same method here.  (Hint you would start by multiplying b+4 by b^2 ).

Or, step by step like this:

I think people would be more likely to read this through if you supplied a picture with it (just providing a link isn't so effective).