posted by Layla on .
A math teacher drove by a playground that was full of boys and dogs.The teacher notice there were a total of 40 heads and 100 feet. Hom many boys and how many dogs were there?
Let x = boys and y = dogs
x + y = 40, then x = 40-y
2x + 4y = 100
Substitute 40-y for x in second equation and solve for y. Insert that value into the first equation and solve for x. Check by inserting both values into the second equation.