Question 1121171
If n counts each $5 increment
<pre>
PRICE    QUANTITY SOLD
 80         20
 80-5       20+6
 80-2*5     20+2*6
 80-3*5     20+3*6
.
.
80-5n      20+6n
</pre>


Revenue to be $2240,
{{{(80-5n)(20+6n)=2240}}}
Simplify and solve.
n is how many $5 increments to remove from $80.