Question 973730
x, the weight of salt in the initial mixture.
{{{x/72}}} the FRACTION of the salt in the initial mixture.


First adjustment:
{{{(x-(x/72)*18)/72}}}


Second adjustment:
{{{((x-(x/72)*18)-((x-(x/72)*18)/72)*18)/72=0.05}}}
Constructing this equation is really the biggest part of solving the problem.  Solving the equation is just arithmetic calculation with the use of just one variable.  Try carefully multiplying left and right members by 72, simply after each step, and keep this up as necessary until you have no more complex fractions.