Median is the middle of the number set so
5 8 10 20 25 30 35 40 45
its 25
<em><u>Tony has 24 books in total</u></em>
Half of 2/3 is:

This means that 1/3 was left. This also means that they ate 1/3 of the lasagne.
Model diagram can be seen in attachment.
They probably want 880 pesos, since they asked you do intermediate rounding
but a more accurate answer would be
883.20 pesos
To combine the functions, you'd substitute in 2.76r for y in 0.16y. This would give you 0.16(2.76r), which simplifies to 0.4416r, but they want you round this to the nearest hundredth, so its really 0.44r. Substitute in the 2000 for r and you get 0.44 * 2000 which is 880 pesos