25/5 would be 5 as a whole number
42n, you can't take the "n" away. The "n" means times a number, so I I write n=2, then the expression will be 42 x 2, substitute the n with a 2
The 7th day is going to be 15.6 there is a common scale factor of timing by 2 the difference between the days so you would get 15.6
The best choice would be the option 3cm
