They ask me that all the time ;)
Let <em>x</em> be the amount of salt in the solution.
At day's end, the concentration of salt in the beaker is
<em>x</em> / (4 L) = 0.08 = 8%
Solve for <em>x</em> to get
<em>x</em> = 0.08 (4 L) = 0.32 L
So at the beginning, the concentration of salt in the beaker was
(0.32 L) / (5 L) = 0.064 = 6.4%
1) 10%
2)12%
3)20%
4)8%
5)50%
Isolating variables mean to get the variable, or the letter all by itself by doing something to get rid of the number/numbers that are on the same side. That way you can solve for that missing variable.
