The minimum cost for 20 crates would be 68 dollars. You would buy 18 crates using the 3 for 10 dollars ( this would cost 60 dollars), and then 2 crates using the one crate for 4 dollars (this would cost 8 dollars) all together you would have 20 crates, costing you 68 dollars.
All direct proportional graphs go through the origin (0,0). So this is where one point could go. The second point is found by going up 5 units and then to the right 3 units to get to (3,5)
<h3>Draw a straight line through (0,0) and (3,5) to graph</h3>
