Question 106094
{{{R=10B+20C+20E}}}
{{{X=20B+60C+10E}}}
{{{F=10B+20C+40E}}}
where R is regular pill, X is extra-strength pill, and F is fortified pills. 
Let's say I take "m" R pills, "n" X pills, and "p" F pills to achieve 50 units of B, 120 units of C, and 90 units of E. 
{{{mR=10mB+20mC+20mE}}}
{{{nX=20nB+60nC+10nE}}}
{{{pF=10pB+20pC+40pE}}}
{{{mR+nX+pF=50B+120C+90E}}}
Therefore equating units of B,C, and E,
{{{10m+20n+10p=50}}}
{{{20m+60n+20p=120}}}
{{{20m+10n+40p=90}}}
Good luck with the solution.