B=book
a=backpack
b=50
b=2a-20
50=2a-20
2a=75
a=37.5
it cost $37.5
In any scientific paper you can find th eprocedure part which should in detail explain how the procedure of a particular experiment was performed. Using these instructions we should be able to replicate an experiment, if the results that were obtained in the previoues experiments were correct of course.
The answer is 1000% D) Plant cells, take in small molecules through the cell membrane