Question 1179222
<pre>
PRICES         COUNTS           COSTS
  8              e               8e
 10            420-e-t          10(420-e-t)
 12              t              12t
               420               3920
</pre>
{{{system(e+420-e-t=5t,8e+10(420-e-t)+12t=3920)}}}


First equation gives {{{highlight(t=70)}}}.


Second equation simplifies to {{{e-t=140}}}.
Substitution gives {{{highlight(e=210)}}}.


Quantity of $10 tickets by difference, {{{highlight(140)}}}.