If 200 pounds of potatoes cost $350, what are the prices of 1 pound of potatoes and 300 pounds of potatoes?

This problem is simply solved by division:
You know 200 pounds of potatoes=350 bucks. You want to first find out how much each potato itself costs. Just from eyeballing it, i can tell you it will be less than $2 (would be 400 potato's), but more than $1.50 (would be 300 potato's

Let's take 350, and divide it by 200, as you divide the cost by the pounds here. 350/200=1.75. This means EACH potato costs $1.75. Now you take this, and multiply it by the 300 pounds. 300*1.75=525

This means if 200 pounds of potato's costs $350:
1 pound costs $1.75
300 pounds costs $525
~Hope this helps!