Question 1179962
<pre>
COFFEE          PRICE       QTY        COST
A                14.99       a         14.99a
B                12.45       b         12.45b
C                 9.95      2a        9.95*2a=19.9a
MIX             11.91        53
</pre>
{{{system(14.99a+19.90a+12.45b=11.91*53,3a+b=53)}}}


Simplify E1.  Use E2, substitute for b in E1 and solve for a.  
Use a to evaluate the other two coffees quantities.