Eleven - fifth teen of the students
Right triangle can be rotated to create a cone!
The rate a computer works is 1/time. Working together, you add the rates.
Let new computer be x, old computer be y.
x = y - 7

Rounded to nearest tenth gives:
x = 23 hours
Sqrt 363 - 3 sqrt27
= sqrt(121* 3) - 3 sqrt (9*3)
= sqrt 121* sqrt3 - 3 * sqrt 9 * sqrt3
= 11 sqrt3 - 3* 3 sqrt3
= 11 sqrt3 - 9 sqrt3
= 2 sqrt3 Answer