So the train is pulling about 50 cars in total, and there's about 30 boxes of freight in each car.
30 x 50 = 1500
The best estimate would be near 1500 boxes of freight through the whole train.
I plugged it into my calculator and I got 1,870.
When you see a "%" you need to ask " a percent of what"?
Here, it's a percent of the original prize, so the discount is 20% of the original prize, that is 20% of 35.
20% is also 20/100 or 1/5, so we can calculate this like this:

so the discount is 7 dollars.