In the function declaration, there is no need for the semi colon after the closing curly bracket.
First box under naming collisions should call
and the quotes either side of the word
should both match.
Methods of an object can be accessed using square bracket syntax
var roomsFree = hotel['checkAvailability']()
Class name on last line should be
elGym.className = hotel.gym
elGym.className = 'Gym: ' + hotel.gym
- same issue two lines above.
On the last line, scientific notation for the number 3,750,000,000 should say 3.75e+9 (not 3.75e+12).
tags, the second and third titles should say
3 decimal places