80 is the answer to your problem
A = allowance
(1/2)a = what have left after Monday
(1/2(1/2)a = what you have after Tuesday
(1/2)(1/2)(1/2)a = what you have after Wednesday.
Doing the multiplication.
(1/8)a = what you have left.
You have 1/8 of what you had at the start.
it would be 0.254.
you have to convery the millimeter to meters
