In 1999, there were 200,000 registered dogs that were Labrador retreivers and dachshunds. There were three times as many Labrador retreivers as dachshunds. Find the number of Labrador retreivers and dachshunds.
Let x = # of retrievers and y = # of dachshunds.
x = 3y
x + y = 200,000
Substitute 3y for x in the second equation and solve for y. Put that value in the first equation to find x. Check by putting both values in the second equation.