The answer would be .5 mols because you take the total amount of grams, which is 20, and you had up the molar mass of sodium hydroxide, which would be 40. After you have this you would set this up as a stochiometry equation. With 1 mol on top you dived 20/40 to cancel out your grams. This leaves you with .5 mols
Planets, black wholes gravity
1 tablespoon = 0.5 ounces
We are required to find for 2 table spoons.
2 table spoons = 2 x 0.5 = 1 ounce.
Each bottle has 16 ounce.
Number of bottles = 4
So total number = 4 x 16 = 64 ounces.
Number of 2 table spoons = 
= 64
Thus there are 64 2-tablespoon doses are in 4 bottles of medication containing 16 ounces each.
Sapphire.
It is a stone not a metal.