Question 133232
First he gives x/2+2 (he has after that x/2-2)
he gives then (x/2-2)/2+2=x/4+1 (he has after that x/4-3)
he gives then (x/4-3)/2+2=x/8+1/2 (he has after that x/8-7/2
then x/8-7/2=1 
then x/8=9/2
x=36


check:
gives 0.5(36)+2=20 then he has 16
gives 0.5(16)+2=10 then he has 6
gives 0.5(6)+2=5 then he has only 1 plant