Question 8000
Let C = the number of chickens and R = the number of rabbits.

Then: 2C + 4R = 360  The total number of legs.
and: C + R = 105  The total number of animals.  Rewrite this as: C = 105 - R and substitute into the first equation.

2(105 - R) + 4R = 360  Simplify and solve for R, the number of rabbits.

210 - 2R + 4R = 360  Add the R's.
210 + 2R = 360  Subtract 210 from both sides.
2R = 150 Divide both sides by 2.
R = 75  There were 75 rabbits.