In the second case, the number of newspaper subscriptions per day is 6 1- 100, so all of them can be sold out in 20 days, and only 60 copies can be sold in 10 day, leaving (x-60) copies at a loss.
The profit from selling is: (5-3.5) * 20 * x+(5-3.5) * 60 *10.
Losses that cannot be sold: (3.5- 1)*(x-60)* 10.
Subtracting the above two formulas is net profit.
In the third case, if the number of newspaper subscriptions per day exceeds 10 1, then 100 can be sold in 20 days, the remaining (x- 100) can be sold in 10 days, and the remaining (x-60) can be sold.
Similarly, the profit from selling newspapers is: (5-3.5) *100 * 20+(5-3.5) * 60 *10.
The loss is: (3.5-1) * (x-100) * 20+(3.5-1) * (x-60) *10.
Just subtract the two expressions.
Additional notes:
(5-3.5) is the profit from selling a newspaper;
(3.5- 1) is the money lost by newspapers that cannot be sold;
Each formula uses the same format:
The profit of a newspaper × the number of newspapers sold in a day× the number of days.
The loss of a newspaper x the number of newspapers left in a day x the number of days.
It's already verbose. If you don't understand, study it slowly.