Sara's results probably do have a higher mean, if we take into account how William is way more willing to pay 20 dollars. Honestly, I think you got your chosen answers right! Just my opinion, as someone inexperienced.
yes
A rational number is a number which can be expressed in the form
where a and b are integers
now 2. 34 = 2
=
→ a rational number
X-13y is the answer to that equation