We can say that the other number is even or it is 0.
The x intercepts occur when you set the factors equal to 0. x+1=0 & x-6=0 gives you the x-intercepts. x+1=0 -> x=-1. x-6=0 -> x=6. Therefore, -1 & 6 are your x intercepts
In Cartesian coordinates, the region is given by

,

, and

. Converting to cylindrical coordinates, using

we get a Jacobian determinant of

, and the region is given in cylindrical coordinates by

,

, and

.
The volume is then
30% = 3/10
Number of hours you sleep = 24hours × 3/10
= 24hours ÷ 10 × 3
= 2.4hours × 3
= 7.2hours
Hope this helps! :)