Nana has a water purifier that filters \dfrac13
3
1

start fraction, 1, divided by, 3, end fraction of the contaminants each hour. She used it to purify water that had \dfrac12
2
1

start fraction, 1, divided by, 2, end fraction kilogram of contaminants.

If you need an equation, it would be y=2x+8, y would be how long it grew, x being weeks.if you need how long he was asleep, it would be 4 weeks if he started with no beard, the equation would be x=8÷2if he did have a beard before hand, the equation would be 2w+x=8