Alex stocks up for winter. he buys 36 cans of vegetables. he paya 80 cent per can for tomatoes and 40 cents per can for corn, for a total cost of $20.8. how many cans of corn does he buy?

If  each of the 36 cans of vegetables were corn the cost would be 0.40*36 or $14.40. This is obviously not enough. For every tomato can you buy instead of corn the price goes $0.80 -$0.40 or $0.40 up. Knowing this all you need is to find how many corns to replace. To do this find the difference between the real cost and the all corn cost. This is $20.8-$14.4 or $6.40. Now to find the number of corns to be replaced just divide this by 0.40 to get 16. That means 16 corns need to be replaced by tomatoes. So there is 20 cans of corn and 16 cans of tomatoes. The answer is 20 cans of corn.