algebra
posted by mary .
there are people walking their dogs at a park. There are 30 heads and 68 feet at the park. Write out the algebraic equations for this problem. Use P to stand for the number of people and D to stand for the number of dogs.

D + P = 30, therefore D = 30P
4D + 2P = 68
Substitute 30P for D in second equation and solve for P. Insert that value into the first equation and solve for D. Check by inserting both values into the second equation.