order the group of quadratic functions from widest to narrowest graph.
y=1/3x^2
y=-3/5x^2
y=8/3x^2

A coefficient in front of the x will stretch the graph to make it wider or narrower. 
A larger coefficient will make the graph narrower, and a smaller coefficient will make the graph wider. 
This is because a larger coefficient results in a larger y value, for example coefficient of 1 in front of x^2 will make coordinate (1,1) but a coefficient of 2 in front of x^2 will make the coordinate (1, 2). As you can see a higher coefficient makes the graph higher, and therefore more narrow. 
From widest to narrowest, it would be 
y = (1/3)x^2,
y = (-3/5)x^2,
y = (8/3)x^2, 
because 1/3 < 3/5 < 8/3