Margot is studying the yield of bushels of wheat in comparison to the amount of rainfall, in inches, that occurs. she finds the linear regression equation to be y = 47.3 +0.78x.
if an additional 1 inch of rain fell, how many more bushels of wheat would be yielded?

Let y be the yield of bushels of wheat in comparison to the amount of rainfall
Let x be the amount of rainfall that occurs (in inches)

If the linear regression equation is y = 47.3 + 0.78x, then per inch of rainfall will yield an addition 0.78 bushels (plugging into x the additional inches of rainfall). 

Therefore, on the first inch of rainfall, y = 48.08. 
On the second inch of rainfall, y = 48.86.

And so on.