Question 345424
(salt I end up with)/(total liters of solution) = 4%
8 milliliters of 6% saline solution has .06*8=.48 ml salt
Let w = ml of water to be added
so....
(0.48)/(8+w)=0.04

Since the variable is in the denominator on the left-hand side of the equation, this can be solved as a ratio.  For example, (A)/(B)=C is equivalent to (A)/(C)=B.
(0.48)/(0.04)=(w+8)

Since w is on the right-hand side of the equation, switch the sides so it is on the left-hand side of the equation.
(w+8)=(0.48)/(0.04)

Remove the parentheses around the expression w+8.
w+8=(0.48)/(0.04)

Reduce the expression (0.48)/(0.04) by removing a factor of  from the numerator and denominator.
w+8=12

Since 8 does not contain the variable to solve for, move it to the right-hand side of the equation by subtracting 8 from both sides.
w=-8+12

Add 12 to -8 to get 4.
w=4 liters