Me ! farmer james has three types of cows on his farm. a cow with zero legs is called a ground beef, a cow with one leg is called a steak, and a cow with two legs is called a lean beef. farmer james counts a total of 20 cows and 18 legs on his farm. how many more ground beefs than lean beefs does farmer james have ?

Lets say that the number of ground beef are x
number of steak - y 
number of lean beef - z
the total number of cows are x + y + z
the total number of cows are 20
Therefore, 
x + y + z = 20 ---1)
the number of legs from ground beef - x * 0 = 0
number of legs from steak - y * 1 = y
number of legs from lean beef - z * 2 = 2z
total number of legs are 18 
0 + y + 2z = 18
y + 2z = 18  2)
y = 18 - 2z
substituting y in 1st equation 
x + (18 - 2z) + z = 20
x + 18 - 2z + z = 20
x - z = 2
We are asked to find how many more ground beef than lean beef, that's x - z
as we calculated x - z = 2.
This means there are 2 more ground beef than lean beef